Colorectal cancer

Colon cancer currently ranks third among other types of cancer.

Colon cancer accounts for 98-99% of all intestinal cancers, mainly adenocarcinoma, less common are solid, mucous and scirrhous forms.

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Epidemiology

In the United States, colon cancer was the second most common cancer after malignant skin tumors. Among other malignant lesions of the colon, malignant tumors predominate, accounting for 95-98%, according to various authors.

Colon cancer varies greatly across the world, with the lowest rates in Africa (1.6-5.9 cases per 100,000 people), average rates in Southern and Eastern Europe (23.6-33.8 cases per 100,000 people), and the highest rates in Western Europe and North America (46.3-51.7 cases per 100,000 people).

In terms of time trends, there has been a decline in incidence in recent years in the United States and European countries such as Portugal, Greece, Italy and Spain. At the same time, most developing countries have seen an increase in the incidence of these tumors in both men and women.

Colon cancer affects men twice as often as women. The most common tumor localization is the sigmoid colon (25-30%) and, especially, the rectum (about 40%), some authors indicate a fairly high frequency (based on their observations) of cancer of the cecum. All other sections of the colon are affected by cancer much less often. These data differ slightly among different authors, but insignificantly - from 3 to 6-8% (for the ascending section of the colon, hepatic and splenic curvature, transverse colon and its descending section).

Colon cancer is much less common in Africa, Asia and South America than in Europe and North America, which is probably due to economic problems and the still lower life expectancy in the above-mentioned regions (and colon cancer occurs mainly in older people). It is also believed that in economically more developed countries, the higher incidence of colon cancer is due to a number of nutritional features, which is confirmed by studies by a very large number of authors (higher consumption of animal fat and meat, some food preservatives, etc.), as well as the release of certain toxic substances into the air and water by industrial enterprises, which have a carcinogenic effect.

In explaining the differences in the frequency of colon cancer in regions of the globe, some differences in the bacterial flora inhabiting the colon of different peoples are also important, explained by nutrition, the preferential consumption of certain foods, and this, as is known, largely determines the nature of the intestinal flora, some species of which may possibly secrete substances with carcinogenic action in the course of their life activity. Apparently, the traditions of culinary processing of food in different peoples are also important.

At the same time, it has been established that carcinogenic substances found in very small concentrations in some food products (aflatoxins, N-nitro compounds, polycyclic aromatic hydrocarbons, etc.), and carcinogenic substances that may arise during the preparation of this food, systematic consumption of these products usually increase the incidence of esophageal, gastric and liver cancer and have little effect on the increase in colon cancer. Therefore, it can be assumed that some types (strains) of bacteria produce carcinogenic substances in the course of their vital activity from those completely "benign", i.e. not possessing a carcinogenic effect in themselves, products of food digestion that reach the colon and are retained in it for a long time (until the next bowel movement). Indeed, some strains of bacteria are capable of producing carcinogenic and mutagenic substances (methylazoxyethanol, volatile phenols, pyrrolidine, etc.) and contain the corresponding enzymes. The production of carcinogenic substances in the colon by these microorganisms depends on the nature of the diet; thus, an increase in the content of bran in food helps to reduce the production of carcinogenic substances and reduce the incidence of colon cancer.

There is a suggestion that in some peoples who eat predominantly plant foods that have a large volume, bowel movements occur more frequently than in the inhabitants of Europe and North America, as a result of which the time of contact of possible carcinogenic agents with the mucous membrane of the colon is reduced, their absorption is reduced, and hence the frequency of carcinomatous lesions of the colon is reduced.

On the other hand, there is an opinion that constipation predisposes to the occurrence of colon cancer. However, since colon cancer is more common in old age, as is constipation, it is difficult to isolate the specific influence of each of these factors on the frequency of carcinogenesis.

Colon cancer can occur at any age, including childhood and adolescence. However, it is most often detected in older age groups: at 60-69 years and 70-79 years - 28 and 18%, respectively. It is interesting to note that in people of the oldest age group (80-89 years and older), its frequency again decreases sharply, approaching that of young people; the reasons for such dynamics of cancer frequency in elderly and old people are unclear.

Thus, the study of the epidemiology of colon cancer and the age-related characteristics of its incidence does not allow us to express sufficiently clear and convincing opinions about the etiology and pathogenesis of this disease.

If we try to link the occurrence of malignant tumors with some local changes in the affected organ, then first of all we should keep in mind chronic inflammatory processes and so-called precancerous diseases.

Against the background of non-specific ulcerative colitis in the USA, Great Britain and Scandinavian countries, the probability of developing colon cancer increases by 8-30 times, and it occurs at a younger age than in the general population (on average 20 years earlier); the 5-year survival rate of these patients after surgery is almost 3 times lower.

The importance of the hereditary factor is undoubted, in particular, many cases of colorectal cancer in descendants have been described, in whose families cases of this localization of malignant tumor were observed in the past. In some forms of hereditary familial polyposis (Gardner syndrome, familial juvenile polyposis of the colon), the degeneration of polyps into cancer, judging by the literature, is observed with an extremely high frequency - up to 95% and higher.

Of the industrial hazards, the dependence of the frequency of colon cancer on asbestosis is most clearly revealed. Undoubtedly, chronic radiation exposure is also important for the development of malignant tumors, including those of the colon.

A special form of colon cancer is noteworthy - the so-called primary multiple cancer (simultaneous occurrence of cancerous tumors of various localizations, in this case in the colon), which occurs, according to various authors, in approximately 5% of cases. The simultaneous occurrence of tumor foci in several areas indirectly indicates a single cause for their origin.

Thus, despite the abundance of hypotheses, the causes and pathogenesis of colon cancer, as well as cancer in general, remain unclear, although all the above facts and assumptions can to a certain extent explain the higher incidence of cancer in some regions compared to others.

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Causes colon cancer

Some researchers believe that colon cancer “occurs only in pathologically altered tissue of the mucous membrane – as a result of inflammatory, erosive-ulcerative, cicatricial processes, which leads to a pathological reaction of the epithelium and contributes to the development of a tumor.”

It has been established that adenomas of the large intestine can cause cancer development. At the same time, a number of authors note an interesting dependence: the larger the size of the adenoma, the greater the probability of its malignancy; the greatest risk of malignancy is for so-called villous adenomas.

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Risk factors

Dietary factors play an important role in the development of colon cancer, especially the consumption of animal fat, the absence of plant fibers in food, and a sedentary lifestyle. As a result, a small amount of chyme enters the colon (which reflexively reduces the motor activity of the intestine) with a high content of bile, fatty acids, and neutral fats. These changes in the chemical composition of the intestinal contents, which slowly move through the intestine and are in prolonged contact with the mucous membrane, in addition to the direct irritant effect, cause disturbances in the microflora, which in turn changes the composition of enzymes of microbial origin (beta-glucuronidase, alpha-dehydrooxidase, etc.). The indicated changes in general are associated with an increase in the frequency of functional, inflammatory and, most importantly, neoplastic processes in the colon.

Recently, some substances have been thought to have protective properties against colon carcinogenesis.

These include: ascorbic acid, selenium, vitamins A, beta-carotene, vitamin E.

Hereditary factors also play an important role in the development of approximately 20% of colorectal cancer cases, increasing the risk of its occurrence by 2-3 times in blood relatives.

Ulcerative colitis is a well-established risk factor for colorectal cancer. If the disease lasts more than 20 years and the entire colon is affected, the probability of developing a tumor increases to 24%.

Precancerous conditions also include polyps, diffuse familial polyposis of the colon, Gardner syndrome, Peutz-Jeghers syndrome, Turk syndrome, Cronkite-Canada syndrome, familial juvenile polyposis, as well as villous adenomas, diverticulosis, Crohn's disease, pararectal fistulas (1% of cases), and chronic untreated anal fissures.

The detection rate of adenomatous polyps of the colon ranges from 1.6 to 12%. During a full colonoscopy, polyps and villous tumors are detected in 20-50% of people over 50 years of age, and the older the age group, the higher the detection rate. Solitary adenomatous polyps are considered an optional precancerous disease, and diffuse adenomatosis is an obligate precancerous disease.

There is a slow development of polyps from the simplest structure to various degrees of atypia and dysplasia of the mucous membrane up to the development of cancer (in 70% of cases). This process takes at least 5 years, and on average lasts 10-15 years. The malignancy index for single polyps is 1:35, for multiple - 1:3.

Villous tumors are exophytic formations of a round or elongated shape, with a characteristic velvety surface. This is due to the abundance of villi. As a rule, a villous tumor is solitary. There are nodular and creeping forms of villous tumors. The nodular tumor is located on a wide base, sometimes turning into a stalk. The creeping form does not have a single tumor node.

Diffuse polyposis appears in prepubertal age, but the full development cycle ends at 20-25 years, and by the age of 40, its malignancy occurs in 100% of cases. Hereditary adenomatosis of the colon is characterized by a high potential for malignancy. In untreated cases, death occurs on average at the age of 40-42, i.e. almost 25 years earlier than with ordinary colorectal cancer.

Peutz-Jeghers syndrome is a total polyposis of the colon, combined with melanin pigmentation on the skin of the face (cheeks, around the mouth), the mucous membrane of the lips and oral cavity, the skin of the back of the fingers and small joints, around natural openings. Colorectal cancer develops in approximately 38% of cases with this syndrome.

In patients with familial polyposis, Turk syndrome involves medulloblastomas and glioblastomas (tumors of the central nervous system). The clinical picture is dominated by neurological symptoms, and only then by polyposis symptoms.

Gardner's syndrome, described in 1953, is characterized by a combination of adenomatous polyps of the colon, dental anomalies, multiple osteomas of the jaws and skull, multiple soft tissue tumors (mainly fibroma type); many patients have multiple fibromas in the mesentery of the small intestine, lipomas of the subcutaneous tissue and other areas.

External manifestations of Gardner syndrome often precede the development of polyps by 10-20 years. Approximately 10-15 years after the appearance of colon polyps, cancerous degeneration develops.

Cronkite-Canada syndrome is a non-hereditary polyposis of the gastrointestinal tract of adults associated with skin hyperpigmentation, patchy vitiligo, alopecia, nail dystrophy, edema, tetany, glossitis, and cataracts.

The etiology of this syndrome is unknown. Infection or immune deficiency are suspected. The clinical picture is characterized by proteinuria, alopecia, skin pigmentation, and changes in fingernails and toenails. Albumin loss is associated with increased mucus production and multiple necroses of polyp tips. Clinically, this is manifested by diarrhea, weight loss, abdominal pain, anorexia, weakness, periodic bleeding during defecation, and vomiting. Mortality is 60%. Colorectal carcinomas develop in 15% of patients.

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Pathogenesis

Most often, cancer develops in the sigmoid colon (50% of cases) and cecum (15% of cases), less often in other sections (ascending colon - 12%, right flexure - 8%, transverse colon - 5%, left flexure - 5%, descending colon - 5% of cases).

In the rectum, the ampullary section is most often affected by cancer (73.8% of cases), less often the supraampullary section (23.3% of cases) and anal section (2.9% of cases).

Colon cancer occurs in the mucous membrane. The tumor spreads along the intestinal wall slightly. Beyond the visible borders, even with endophytic cancer, it is detected at a distance of no more than 4-5, more often 1-2 cm.

After all layers of the intestinal wall have grown through, the tumor process then spreads to surrounding tissues and organs. A strand of the greater omentum, the small intestine, or its mesentery may become attached to the area of the large intestine affected by the tumor.

Following the development of inflammatory adhesions, tumor infiltration into the organs fused to the colon occurs. Often, tumor spreads toward the mesentery of the colon. In men, rectal cancer most often spreads to the seminal tubercles and prostate gland, and in women - to the uterus and vagina.

A specific feature of colon cancer is the rather long local spread of the tumor (including growth into surrounding organs and tissues) in the absence of metastasis to regional lymph nodes, which may appear quite late.

Colon cancer is divided (A. M. Ganichkin) into two large groups according to its macroscopic structure: 1) exophytic and 2) endophytic.

The following forms of colon cancer are considered exophytic:

1. polyp-like tumor on a stalk;
2. nodular, broad-based, mushroom-shaped, protruding into the intestinal lumen; may ulcerate;
3. villous-papillary, cauliflower-shaped, consisting of several nodes of various sizes.

In the rectum, a plaque-like tumor is also distinguished, when a flat node in the upper central section has the same dimensions as at the edges. It has a flat or even concave surface.

The following endophytic forms of colon cancer are distinguished:

1. ulcerative in the form of a flat ulcer with clear raised edges; can circularly cover the intestine, stenotic its lumen;
2. diffuse-infiltrative, infiltrating the entire thickness of the wall of the colon without clear boundaries, causing narrowing of the lumen.

Exophytic forms of cancer are more common in the right half of the colon, are nodular, polypoid and villous-papillary; the tumor grows into the lumen of the intestine. Endophytic tumors are more common in the left half of the colon. They are saucer-shaped and diffusely infiltrative, in the latter case they often circularly cover the intestine and narrow its lumen.

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Symptoms colon cancer

Colon cancer has various symptoms, they depend on the structure and localization of the tumor. The initial period ("early cancerous tumor") is usually asymptomatic and if detected, then mainly only during a routine examination or during a rectoscopy, colonoscopy, irrigoscopy or digital examination of the intestine, undertaken for another suspected or existing disease of the colon.

Somewhat later, when colon cancer reaches a fairly large size and the first signs of cancer intoxication and some symptoms indicating difficulty in moving contents through the colon appear, a number of general non-specific symptoms are noted, such as unmotivated weakness, loss of appetite, weight loss, "intestinal discomfort" (heaviness after eating, bloating and vague pain in the abdomen, rumbling, flatulence, unstable stool, etc.). Later, the symptoms of tumor damage to the intestine become more distinct.

Colon cancer on the right often occurs with intestinal bleeding, hypochromic anemia, and often pain. In some cases, palpation can detect a nodular tumor, which, despite its fairly large size by this time, usually does not obstruct the intestine, so symptoms of intestinal obstruction are uncommon for this tumor localization. This is also facilitated by the liquid contents of the right half of the colon, which freely passes through the narrowed area.

Colon cancer on the left often forms a ring-shaped narrowing of its lumen; the tumor is less often palpated, can cause cramping pain in the abdomen, alternating diarrhea and constipation, sometimes a picture of partial obstructive obstruction. In this case, limited bloating of the left half of the abdomen and visible intestinal peristalsis are noted. In some cases, feces acquire a ribbon-like shape or the appearance of "sheep feces". Pain occurs earlier when the tumor is localized in the anal ring, when it is localized in the ampulla of the rectum, it appears at a later period. Tumors of the anus are accompanied by defecation disorders. Tumors of the distal rectum are easily detected by digital examination.

Symptoms of colon cancer are characterized by five main syndromes:

1. functional symptoms syndrome without intestinal disorders;
2. with intestinal disorders;
3. intestinal obstruction syndrome;
4. pathological discharge syndrome;
5. violations of the general condition of patients.

The first syndrome includes abdominal pain and intestinal discomfort (loss of appetite - sorting through food, nausea, belching, unpleasant sensations in the mouth, single vomiting, bloating and a feeling of heaviness in the epigastric region).

Abdominal pain occurs in the majority of patients (up to 90%) - the first symptoms of colon and large intestine cancer. The pain can be constant, pressing, aching, sometimes cramping. The reverse throwing of intestinal contents due to the disruption of the motor function of the ileocecal locking apparatus leads to spastic contractions of the ileum, which is clinically manifested by pain in the right iliac region.

The inflammatory process in the tumor itself and around it can also cause pain. When pain is localized in the area of the hepatic flexure, transverse colon, differential diagnosis should be made with cholecystitis, exacerbation of peptic ulcer disease. If pain is localized in the right iliac region, acute appendicitis should be excluded.

Initial symptoms of colon cancer colon cancer - intestinal discomfort: nausea, belching, unpleasant drooping in the mouth, vomiting, periodic bloating, a feeling of heaviness and fullness in the epigastric region. The listed symptoms of colon cancer focus the attention of patients, and often doctors, on diseases of the stomach and gallbladder.

The phenomena of intestinal discomfort are explained by the neuro-reflex connections of the ileocecal region with other organs of the abdominal cavity. The inflammatory process accompanying the cancerous tumor, as well as the absorption of decay products, intestinal contents through the altered mucous membrane of the colon lead to functional disorders of the stomach, duodenum and pancreas, which are expressed by the same symptoms.

The intestinal disorder syndrome includes symptoms of colon cancer indicating severe dysfunction of the colon: constipation, diarrhea, alternating constipation with diarrhea, bloating and rumbling in the abdomen. The cause of intestinal disorders is impaired motor function, paresis, or, conversely, accelerated intestinal peristalsis.

Clinical signs of intestinal disorders are most often observed in cancer of the left half of the colon. This is due to the fact that endophytic tumors of the left half quickly lead to narrowing of the affected area of the intestine.

The progression of the tumor process leads to narrowing of the intestinal lumen and disruption of intestinal patency. Since the diameter of the lumen of the right sections of the colon is almost 2 times larger than the diameter of its left sections, narrowing of the intestinal lumen in cancer of the right half and disruption of intestinal patency occurs much more slowly, with the exception of a tumor of the ileocecal valve, where obstruction can occur quite early.

Therefore, intestinal obstruction most often complicates (in approximately 73% of cases) cancer of the left half, and less often cancer of the right half of the colon.

Complete obstruction in the tumor area is rare, but signs of obstruction appear when the lumen narrows to 1.0 - 0.6 cm. Intestinal obstruction usually develops in the late stages of cancer, but in some cases it is this that brings patients to medical institutions.

Among the symptoms of colon cancer, pathological discharge should be given significant importance. The discharge of blood, mucus and pus with feces during defecation is the most characteristic symptom of rectal cancer, but it can also be observed in colon cancer, especially its left half.

Analysis of clinical observations shows that blood in the stool may be present not only in the late stages of cancer. With exophytic cancer, blood may also appear in the early stages; with endophytic forms, pathological discharge is observed less frequently. Copious discharge in colon cancer is rare. Daily blood loss averages about 2 ml.

Violations of the general condition of patients are observed. Among the early manifestations, such symptoms of colon cancer as anemia, fever, general malaise, weakness and emaciation come to the fore. This picture is most typical for cancer of the right half of the colon, especially the cecum and ascending colon.

Patients with apparent well-being experience general malaise, weakness, increased fatigue and rapid fatigability. Following this, paleness of the skin is noted, blood tests reveal hypochromic anemia, sometimes fever (body temperature 37.5 °C) is the only first sign of colon cancer.

An increase in temperature (up to 39 °C) as an initial symptom is relatively rare among the clinical signs of colon cancer and is apparently caused by inflammatory-reactive foci around the tumor, retroperitoneal tissue, regional lymph nodes, as well as the absorption of tumor decay products.

According to most clinicians, the development of anemia (hemoglobin below 90 g/l) is associated with intoxication as a result of the absorption of tumor decay products and infected intestinal contents, but one cannot exclude neuroreflex effects from the ileocecal section of the intestine, leading to a disruption of the hematopoietic function.

In one third of cancer patients, anemia is the only clinical sign of the presence of a malignant process. Hypochromic anemia as an independent disease can be diagnosed when cancer of the right half of the colon is excluded clinically, radiologically and even surgically.

Weight loss occurs in advanced cancer cases in combination with other symptoms and is of little independent significance. Among the general disorders of the patient's body in cancer, one should also include such a symptom as loss of the plastic properties of connective tissue, expressed by the causeless appearance of hernias of the abdominal wall.

In addition to the five groups of symptoms listed above, attention should be paid to an important objective symptom of colon cancer - a palpable tumor. The presence of a palpable tumor directly indicates a pronounced clinical picture of colon cancer, but this does not mean that radical surgical treatment is impossible. The tumor is determined by objective examination in almost every third patient, more often in cancer of the cecum and ascending colon, hepatic flexure, less often in the sigmoid colon.

Careful and targeted detection of initial clinical manifestations allows not only to suspect, but also, with appropriate detailed examination, to recognize colon cancer in a timely manner.

Course and complications

The course of the disease is gradually progressive. Anemia increases, ESR increases, fever appears, cancer cachexia progresses. Often, mucus and pus appear in the feces. As the tumor grows, it can grow into adjacent intestinal loops, omentum and neighboring organs, and in some cases, due to the reaction of the peritoneum and the occurrence of adhesions, a rather large conglomerate is formed.

The life expectancy of patients without treatment is 2-4 years. Death occurs from exhaustion or complications: profuse intestinal bleeding, intestinal perforation, followed by the development of peritonitis, intestinal obstruction, as well as from the consequences of metastases.

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Stages

There are 4 stages of colon cancer:

1. a small tumor limited to the mucous or submucous layer;
2. a tumor that grows into the muscular layer and even into the serous membrane, but does not have nearby or distant metastases;
3. a tumor that has metastasized to regional lymph nodes;
4. a tumor that spreads to nearby organs or has multiple metastases.

The international classification according to the TNM system more accurately reflects the entire diversity of the primary tumor process and metastasis.

Depending on the size of the primary tumor, Tis (carcinoma in situ) and T1-T4 are distinguished. The absence or presence of metastases in regional and distant lymph nodes is designated as N0-N1 and N4 (categories N2 and N3 are not used); the absence or presence of distant metastases - as M0 and Mi. Histopathological grading of cancer is also used (according to histological examination of biopsies) - Gi, G2 and G3, which means high, medium and low degree of differentiation of cancer cells.

Oncologists use this classification in an even more detailed version.

According to the macroscopic picture, there is an exophytic form of cancer (usually in the right sections of the colon) and endophytic (usually in the left sections of the colon). Exophytic cancer is a nodular tumor, usually sitting on a wide base and growing into the lumen of the intestine, usually it is polypoid or papillary cancer. During growth, the tumor can sometimes cause partial or complete obstruction of the intestine, its surface can become necrotic, leading to intestinal bleeding. Endophytic cancer spreads along the intestinal wall, often enveloping it in a ring-shaped manner, and towards the peritoneum. The tumor is a scirrhus or ulcerative form of cancer. Histological examination most often reveals adenocarcinoma, much less often - solid and mucous cancer.

Metastases to regional lymph nodes are often observed only in the late stages of the disease. Distant metastases are most often found in the liver.

Rectal cancer is most often localized in its ampulla, ulcerative, papillomatous, fungoid and infiltrative forms are encountered. The histological form of rectal cancer can also be different: adenocarcinoma, gelatinous, solid cancer, less often - squamous cell cancer. As the tumor grows, it grows into neighboring organs: the bladder, uterus, sacrum. Rectal cancer metastasizes to regional lymph nodes, spine, liver.

Colon cancer can be localized in any of its sections, but most often in the rectum. The rectum is usually divided into the lower ampullar section, approximately 5 cm, the middle ampullar section (5-10 cm), and the upper ampullar section (10-15 cm). The sigmoid colon is the second most common section, and the colon is the third. In the colon, any of its three sections can be affected, but the tumor is most often located in the hepatic and splenic angles. As a rule, the tumor grows as a single node, but multicentric cancer can also develop, usually genetically associated with polyposis.

Clinical classification of colorectal cancer according to TNM (IPRS, 2003)

T - primary tumor:

Tx - insufficient data to assess the primary tumor;

T0 - the primary tumor is not determined;

Tis - intraepithelial or with mucosal invasion;

T1 - the tumor infiltrates the intestinal wall to the submucosa;

T2 - the tumor infiltrates the muscular layer of the intestinal wall;

T3 - the tumor infiltrates the subserosa or tissue of non-peritonealized areas of the colon and rectum;

T4 - the tumor invades the visceral peritoneum or directly spreads to adjacent organs and structures.

Regional lymph nodes are the paracolic and pararectal, as well as the lymph nodes located along the iliac, right colonic, middle colonic, left colonic, inferior mesenteric and superior rectal (hemorrhoidal), internal iliac arteries.

Nx - insufficient data to assess regional lymph nodes;

N0 - no signs of metastatic lesions of regional lymph nodes;

N1 - metastases in 1-3 regional lymph nodes; N2 - metastases in 4 or more regional lymph nodes. M - distant metastases:

Mx - insufficient data to determine distant metastases;

M0 - no signs of distant metastases; M1 - there are distant metastases.

Grouping by stages

Stage 0 - Tis N0 M0

Stage I

• T1 N0 M0
• T2 N0 M0

Stage II

• TZ N0 M0
• T4 N0 M0

Stage III

• Any T N1 M0
• Any T N2 M0

Stage IV - Any T Any NM

Dukes staging (Dukes stage) G. Dukes (1932) identified four stages of colon cancer:

• A. The tumor is localized in the mucous membrane of the intestinal wall, without growing into other layers. This group includes polypoid, easily removed tumors with an ulcerated surface.
• B. The tumor is ulcerated, grows through all layers of the intestinal wall and is even fixed, but metastases in regional lymph nodes are usually not observed.
• C. The tumor is of the same nature as in group “B”, but with the presence of metastases in the regional lymph nodes.
• D. This group is represented by a primary tumor with metastases to distant organs.

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Clinical classification of anal cancer according to TNM (IPRS, 2003)

T - primary tumor:

Tx - insufficient data to assess the primary tumor;

T0 - the primary tumor is not determined;

Tis - preinvasive carcinoma;

T1 - tumor up to 2 cm in greatest dimension;

T2 - tumor up to 5 cm in greatest dimension;

TZ - tumor more than 5 cm in greatest dimension;

T4 - tumor of any size, growing into adjacent organs: vagina, urethra, bladder (involvement of one muscular sphincter is not classified as T4). N - regional lymph nodes:

Nx - insufficient data to assess regional lymph nodes;

N0 - no signs of metastatic lesions of regional lymph nodes;

N1 - metastases in the perirectal lymph nodes;

N2 - metastases in the iliac or inguinal lymph nodes on one side;

N3 - metastases in the perirectal and inguinal lymph nodes and/or in the iliac and/or inguinal on both sides.

Grouping by stages

Stage 0

• Tis N0 M0

Stage I

• T1 N0 M0

Stage II

• T2 N0 M0
• TZ N0 M0

Stage IIIA

• T1 N1 M0
• T2 N1 M0
• TZ N1 M0
• T4 N0 M0

Stage IIIB

• T4 N1 M0
• Any T N2, N3 M0

Stage IV

• Any T Any NM

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Forms

Classically, according to the proposal of A. M. Ganichkin (1970), six clinical forms of colon cancer are distinguished:

1. toxic-anemic, characterized by the predominance of general disorders and progressive hypochromic anemia;
2. enterocolitic, characterized by a symptom complex of dominant intestinal disorders;
3. dyspeptic, in which functional disorders of the gastrointestinal tract predominate; such patients are often examined with a diagnosis of "gastritis", "peptic ulcer", "stomach cancer", "chronic pancreatitis";
4. obstructive, which is characterized by the early appearance of a symptom complex of intestinal obstruction;
5. pseudo-inflammatory, among the initial clinical manifestations of which the symptoms of the inflammatory process in the abdominal cavity come to the fore: abdominal pain, irritation of the peritoneum and tension of the abdominal wall muscles, increased temperature, increased leukocytosis and increased ESR; this symptom complex is a clinical manifestation of the inflammatory process, often accompanying colon cancer;
6. atypical tumor, characterized by the presence of a palpable tumor in the abdominal cavity with little clinical symptoms of the disease.

Macroscopic forms and growth patterns

Depending on the nature of growth, the following forms of colon cancer are distinguished:

1. exophytic - plaque-like, polypous, large-tuberous;
2. transitional (exo- and endophytic) - saucer-shaped cancer;
3. endophytic - endophytic-ulcerative and diffuse-infiltrative

Exophytic cancers are more often observed in the right half of the colon and the ampullar section of the rectum. Endophytic growth is more typical for cancers of the left half of the colon and the rectosigmoid section.

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Microscopic structure

According to the International Histological Classification of Intestinal Tumours (No. 15 WHO, Geneva, 1981), the following types of colon cancer are distinguished:

1. adenocarcinoma;
2. mucinous (mucous) adenocarcinoma;
3. signet ring cell carcinoma;
4. squamous cell carcinoma;
5. glandular squamous cell carcinoma;
6. undifferentiated cancer;
7. unclassifiable cancer.

Adenocarcinoma accounts for more than 90% of all carcinomas in the colon and rectum. The tumor is built from atypical glandular epithelium, forming various structures - tubular, acinar, papillary. In this case, different degrees of cancer differentiation are possible.

Highly differentiated adenocarcinoma is characterized by histological and cytological signs of normal initial epithelium, while the glandular structures of the tumor are uniform, built from absorptive colonocytes, among which there are Paneth and Kulchitsky cells. There is a sufficient amount of secretion in the lumen of the glands. Poorly differentiated adenocarcinoma is characterized by histological and cytological signs that only vaguely resemble normal epithelium - the cells are extremely polymorphic, a large number of atypical mitoses are noted. Goblet cells are not detected. The glands that form these cells are also distinguished by great diversity. Moderately differentiated adenocarcinoma is a cancer that, according to a set of histological signs, occupies an intermediate position between well and poorly differentiated tumors.

Mucous cancer is an adenocarcinoma characterized by pronounced mucus production. There are 2 types of this tumor. The first type - the tumor has a glandular structure, mucin is contained in the lumen of the glands, the latter resemble "lakes" filled with mucus; in addition, mucin is present in the tumor stroma. The second type - the tumor is built from strands or groups of cells surrounded by mucus. In both types of mucous cancer, it is necessary to assess the degree of differentiation according to the same criteria as in adenocarcinoma.

Signet ring cell carcinoma is a tumor consisting exclusively of signet ring cells, the cytoplasm of which contains mucous contents.

Squamous cell carcinoma in the colon and sigmoid colon is extremely rare. It is found mainly in the transition zone between the rectum and the anal canal. The tumor is built from atypical squamous epithelial cells, which are characterized by intercellular bridges and keratin - intracellular (non-keratinizing cancer) and extracellular (keratinizing cancer). Squamous cell keratinizing cancer is an extremely rare tumor.

Squamous cell carcinoma is an extremely rare tumor variant that consists of two components: adenocarcinoma and squamous cell carcinoma. Small foci of squamous cell transformation are sometimes observed in adenocarcinoma.

Undifferentiated cancer is a tumor built from atypical epithelial cells that do not contain mucus and do not form glands. Tumor cells are often polymorphic, sometimes monomorphic, forming layers and strands separated by scanty connective tissue stroma.

If the histologically detected tumor does not belong to any of the above mentioned and described categories, it is called unclassifiable cancer.

The WHO classification (1981) also identifies a group of tumors of the anal canal and anus. The following histological types of cancer are identified in the anal canal:

1. squamous;
2. basal cell-like cancer (basaloid);
3. mucoepidermoid;
4. adenocarcinoma;
5. undifferentiated;
6. unclassified.

Squamous cell carcinoma often has a nonkeratinizing structure and very rarely - keratinizing. Cancer resembling basal cell (basaloid) is recommended to be called "cloacogenic cancer", according to morphology, it also varies depending on the degree of differentiation. Mucoepidermoid cancer is a combination of mucus-forming, epidermoid cells and intermediate cells. Adenocarcinoma in the anal canal is divided into 3 varieties: rectal type, adenocarcinoma of the rectal glands and adenocarcinoma in the rectal fistula.

To assess the degree of malignancy of colon cancer, in addition to the histological type and degree of differentiation of cancer, the depth of wall invasion, cellular polymorphism, mitotic activity, lymphocytic and fibroblastic reaction of the stroma, and the form of tumor spread should be taken into account.

Colon cancer metastasizes lymphogenously to regional lymph nodes and hematogenously to the liver. In cases of advanced cancer, hematogenous metastases are sometimes detected in the bones, lungs, adrenal glands, and brain. However, as a rule, such localization of secondary tumor nodes is rare, and more often, even in the case of a fatal outcome, the process is limited to liver damage. In some cases, implantation metastases are possible in the form of peritoneal carcinomatosis.

International histological classification of intestinal tumors

Epithelial tumors.

1. Adenocarcinoma (75-80% of cases). According to the International Histological Classification of WHO, the degree of its differentiation is indicated (highly, moderately, poorly differentiated).
2. Mucinous adenocarcinoma (up to 10-12% of cases).
3. Signet ring cell carcinoma (up to 3-4%).
4. Squamous cell carcinoma (up to 2%).
5. Undifferentiated cancer.
6. Carcinoids.
7. Mixed carcinoid-adenocarcinoma.

Nonepithelial (mesenchymal tumors).

1. Gastrointestinal stromal tumor (GIST).
2. Leiomyosarcoma.
3. Angiosarcoma.
4. Kaposi's sarcoma.
5. Melanoma.
6. Malignant lymphoma.
7. Malignant neurilemoma (schwannoma).

Most malignant tumors of the colon have the structure of adenocarcinoma (approximately 90% of patients), less often - mucous adenocarcinoma (mucous cancer), signet ring cell cancer (mucocellular cancer), squamous cell (keratinizing and nonkeratinizing) and undifferentiated cancer.

Complications and consequences

The most common complication is intestinal obstruction, which develops as a result of obstruction of the intestinal lumen by a tumor. It occurs in 10-15% of patients. The development of obstructive obstruction in cancer of the left half of the colon is observed 4-6 times more often than in cancer of the right half. Rarely, intestinal obstruction can be caused by intussusception of an exophytic growing tumor, volvulus of a loop of the intestine affected by the tumor.

Inflammation in the tissues surrounding the tumor develops in 12-35% of patients. In this case, a clinical picture of an abscess or phlegmon develops. If the pathological process is localized in the cecum, it can proceed under the guise of acute appendicitis in the stage of appendicular infiltrate.

Severe forms of clinical course include cancerous tumors complicated by perforation of the intestinal wall (2-5% of cases). Perforation of the tumor may occur in the direction of the abdominal wall or retroperitoneal space, as well as into the free abdominal cavity; in rare cases, indirect perforation of the tumor into the abdominal cavity occurs through a breakthrough of an abscess located around the tumor.

Long-term retention of dense fecal matter can lead to the formation of bedsores in the intestinal wall directly above the tumor and rupture of the wall (diastatic perforation - perforation from overflow). The clinical picture of diastatic perforation is characterized by a particular severity of the course. The increase in the clinical picture of intestinal obstruction with the sudden development of violent peritonitis is an indicator of perforation from intestinal overstretching.

As colon cancer develops, it spreads to adjacent organs (in 15-20% of cases). When the tumor grows into the perirenal tissue, ureter and kidney, dysuric disorders, moderate hematuria and albuminuria are added. When a colon-vesical fistula forms, pneumaturia and even fecaluria may occur.

Invasion of the retroperitoneal part of the duodenum and pancreas is clinically characterized by an increase in pain, the appearance of diarrhea, nausea, vomiting and deterioration of the general condition of the patient. Internal fistulas with colon cancer invasion often open into the small intestine, bladder and stomach, but pathological anastomoses can also form with the duodenum, gall bladder and between different parts of the colon.

When colon cancer spreads to the stomach, patients experience a feeling of heaviness in the epigastric region, nausea, belching, and periodic vomiting. When the uterus and its appendages grow, pain occurs in the lower abdomen, the menstrual cycle is upset, and bloody or mucopurulent vaginal discharge appears.

[ 38 ], [ 39 ], [ 40 ], [ 41 ], [ 42 ], [ 43 ]

Colon cancer metastasis

Metastasis occurs through lymphogenous (30% of cases), hematogenous (50% of cases) and implantation (20% of cases) routes.

The main route of colon cancer metastasis is lymphogenous, with the lymph nodes of the first order, located at the point of attachment of the mesentery to the intestinal wall, being affected first. Subsequently, the lymph nodes in the area of division of the mesenteric vessels are affected, and even later, the lymph nodes of the mesenteric root.

The main zones of regional metastasis of rectal cancer were identified by Miles back in 1908. He showed that the spread of the tumor process occurs in three directions: ascending, lateral and descending.

Lymphogenous spread of rectal cancer occurs along the upper rectal lymphatic vessels to the anorectal nodes, and then to the lymph nodes located at the base of the inferior mesenteric artery and further to the retroperitoneal paraaortic and preaortic lymph nodes. Metastasis of rectal cancer along the middle hemorrhoidal arteries to the iliac lymph nodes is also possible, as well as retrogradely along the lower hemorrhoidal arteries to the inguinal lymph nodes. According to various authors, regional lymph nodes in colon and rectal cancer are affected in 40-60% of cases.

Ascending metastasis involves the pararectal, superior rectal and inferior mesenteric nodes, lateral spread affects the middle rectal, obturator, internal iliac and common iliac nodes, and descending spread affects the inguinal lymph nodes.

A number of patterns of rectal cancer metastasis have been identified depending on the section in which the tumor is localized. It is believed that in the case of cancer of the upper ampullar section, the lymph nodes along the superior rectal, inferior mesenteric arteries and the aorta are most often affected by metastases, in the case of cancer of the lower and middle ampullar sections - the iliac lymph nodes and pelvic nodes, and in the case of anal cancers - the inguinal lymph nodes of the intestine.

Lymphatic metastasis is one of the reasons why the probability of recurrence after rectal cancer surgery is very high. Therefore, in rectal cancer surgery, the lymphatic drainage system has always been considered one of the main targets, the impact on which could improve long-term results.

[ 44 ], [ 45 ], [ 46 ]

Hematogenous metastasis

The hematogenous spread of cancer is based on the process of embolization of venous outflow tracts from organs affected by malignant tumors by cancer cells. Penetration of cancer cells into venous vessels occurs mainly as a result of invasion and destruction of vessel walls by the tumor. As is known, the bulk of venous blood through the superior and inferior mesenteric veins enters the portal vein and only from the distal rectum flows into the inferior vena cava. The indicated anatomical features of the circulatory system of the colon explain why cancers of this localization metastasize mainly to the liver. Synchronous metastases to the liver develop in 10-15% of patients with colon cancer. The second place in the frequency of distant metastasis is occupied by the lungs, and metastases are most often multiple. Metastases to the lungs in colon cancer are found during autopsies of deceased patients in 22.3% of cases.

Less frequently than in the liver and lungs, but still relatively often, colon cancer metastasizes to the bones of the skeleton: to the lumbosacral spine, pelvic bones, ribs, sternum, femurs, collarbone, and brain.

Implantation metastasis

When the entire thickness of the intestinal wall grows and the tumor reaches the serous membrane, cancer cells can be implanted on the surface of the peritoneum, on the surface of the healthy mucous membrane in the proximal or distal parts of the intestine located from the tumor, as well as on the surrounding organs and tissues.

Tumor cells most often adhere to the parietal or visceral peritoneum, soon manifesting themselves as characteristic millet-like multiple rashes on it. The tubercles are dense to the touch and usually have a grayish-white color. Ascitic fluid appears in the abdominal cavity, which is usually hemorrhagic in nature.

Diagnostics colon cancer

The diagnosis of colon cancer has the following main objectives:

• establishing the localization of colon cancer, its extent, anatomical growth pattern and morphological structure;
• determination of local and distant prevalence of the tumor process;
• assessment of the general condition of the patient and the function of vital organs and systems.

Examination of the patient begins with a thorough study of complaints and the history of the disease. During physical examination, attention should be paid to the color of the skin, the condition of the peripheral lymph nodes, especially the inguinal ones. When palpating the abdomen, a tumor-like formation can be detected, as a rule, with large tumor sizes, as well as a painful infiltrate, indicating the addition of inflammation. In emaciated patients, the liver affected by metastases can be palpated.

The objective examination ends with palpation of the rectum, and in women - with vaginal examination. Digital examination is effective in 70% of patients. If the tumor is reached with a finger, then its localization from the edge can be determined, as well as mobility in relation to the surrounding structures.

Rectomanoscopy allows diagnosing cancer of the rectum and lower sigmoid colon, determining its extent, anatomical form of growth, and also taking a biopsy to determine the morphological structure of the tumor.

X-ray examination of the colon allows to identify up to 90% of tumors. Barium sulfate is most often used as a contrast agent. The contrast agent can be taken orally and then its movement through the gastrointestinal tract is monitored using repeated X-ray examinations. Contrast is most often administered by enema. The technique of such an X-ray examination (irrigoscopy) consists of the following stages:

• study of the contours of the intestine when it is tightly filled with contrast;
• study of the relief of the mucous membrane after partial emptying of the intestine;
• examination after introducing air into the intestine (double contrast).

Radiographic signs of colon cancer:

• obstruction of the intestinal lumen with pronounced deformation of the contours;
• narrowing of the intestinal lumen;
• filling defect;
• a flat "niche" in the intestinal contour;
• changes in the relief of the intestinal mucosa;
• absence of peristalsis in the altered section of the intestine;
• intestinal wall rigidity;
• violation of contrast evacuation.

Colonoscopy is an endoscopic method of examining the large intestine. This diagnostic method is available for tumors up to 1 cm in diameter, which are often detected during irrigoscopy. Unfortunately, it is not always possible to perform a full colonoscopy. In this regard, the entire colon should be examined using both colonoscopy and irrigoscopy. This is of particular importance in the case of multiple lesions of the colon, when a distally located tumor narrows the lumen of the intestine and does not allow the colonoscope to be passed beyond the narrowing site. Thus, tumors located above are diagnosed during surgery or, even worse, after it. Visual diagnostics during colonoscopy must be verified morphologically.

Theoretically, the ideal method for assessing the T criterion is endoscopic ultrasound. Ultrasound colonoscopy is proposed as a method for clarifying the diagnosis of epithelial neoplasms of the colon, which allows, according to endosonographic criteria, to differentiate benign and malignant tumors, determine the depth of their invasion into the intestinal wall, and establish the presence of metastases in regional lymph nodes.

With the help of ultrasound colonoscopy it is possible to obtain previously inaccessible diagnostic information in terms of nature, volume and quality:

• detection and assessment based on known endoscopic semiotics of various neoplasms of the colon, determination of their nature, size, type of growth, obtaining tissue fragments for morphological study;
• determination of the absence or presence of tumor invasion (including assessment of its depth) of the detected neoplasm into the thickness of the colon wall;
• determination of the local prevalence of detected malignant neoplasms, involvement of organs and tissues adjacent to the affected area of the intestinal wall, and regional peri-intestinal lymph nodes.

It has been established that the sensitivity of ultrasound colonoscopy in the differential diagnosis of epithelial neoplasms of the colon is 96.7%, specificity is 82.4%.

Correct determination of the depth of tumor invasion of the colon wall is possible in 75.4% of cases, with the best results obtained when establishing T3 and T4 invasion, where the diagnostic accuracy was 88.2 and 100%, respectively.

The accuracy of ultrasound colonoscopy in visualizing regional lymph nodes is 80.3%, sensitivity is 90.9%, specificity is 74.4%. In assessing the nature of visualized pericolonic lymph nodes by ultrasound signs, the diagnostic accuracy is 63.6%.

The resolution capabilities of ultrasound colonoscopy and other instrumental diagnostic methods were studied in a comparative aspect.

In all criteria of efficiency assessment, the ultrasound colonoscopy method is superior to the routine method (accuracy is 9.5% higher, sensitivity is 8.2% higher, specificity is 11.8%). In terms of diagnostic efficiency, ultrasound colonoscopy also surpasses the X-ray method of examining colon neoplasms. The accuracy of ultrasound colonoscopy was 6.7% higher, sensitivity is 20% higher, and specificity is 10%.

Thus, ultrasound colonoscopy is the most informative, non-invasive, repeatable, safe method of objective clarifying diagnostics of epithelial neoplasms of the colon, the diagnostic efficiency of which significantly exceeds that of all routine methods of hardware and instrumental diagnostics used to date in clinical oncology.

The ability of computed tomography (CT) to detect tumor invasion through the intestinal wall is very limited compared to EUS. Indeed, the good sensitivity of CT (82-89%) is accompanied by low specificity (51%), mainly due to the fact that the tumor has an irregularly shaped outer edge surrounded by edematous perirectal adipose tissue, which leads to an overestimation of the stage of spread.

Nuclear magnetic resonance imaging (NMR) cannot assess tumor infiltration of the rectal wall with high accuracy, but, like CT, it gives a good idea of the involvement of surrounding tissues and structures and predicts regional lymph node metastasis in 81–82% of cases.

With respect to the evaluation of the N criterion, specific information can be obtained by EUS, pelvic CT, and MRI. More specific studies such as lymphangiography, interstitial lymphoscintigraphy (with Tc-99t antimony trisulfide colloidal solution injected to a depth of 4 cm into each ischiorectal fossa), rectal lymphoscintigraphy (with Tc-99t - a colloidal stannous sulfide solution injected into the submucosa of the rectum using a special needle through a rectoscope), and rectal immunolymphoscintigraphy with monoclonal antibodies are used to improve the accuracy of diagnosis of lymph node metastasis.

Finally, regarding the assessment of the M criterion, it is known that synchronous liver metastases develop in 10-15% of patients with rectal cancer, manifesting as pain in the right upper quadrant of the abdomen: right hypochondrium, right posterior chest or right shoulder. The pain can be chronic or acute, caused by hemorrhage or necrosis of metastases. Liver enlargement can be diagnosed during routine clinical examination of patients without complaints. Liver echotomography (ultrasound) is the first method in the diagnosis of metastases, although it is less accurate than CT or MRI, especially in patients with diffuse lesions of the liver parenchyma, since fibrosis and scarring of the tissue can hide the presence of small tumors. However, CT and MRI should not be used when there are no clear indications. Patients in whom liver metastases are detected by ultrasound should undergo preoperative percutaneous needle biopsy for better planning of surgical treatment.

To plan treatment and determine the prognosis of the disease, it is necessary to determine the characteristics of the biological aggressiveness of tumors with different growth rates, and, consequently, different kinetic and clinical characteristics.

The most important here are operational markers such as CEA, differentiation degree, cell proliferation indices, DNA ploidy. The carcinoembryonic antigen (CEA) test is useful and is the basis for patient monitoring and helps in prognosis. Indeed, there is a clear correlation between the preoperative CEA level, differentiation and the stage of the disease. In highly differentiated tumors, an increase in CEA is observed in 61% of cases, and in poorly differentiated tumors only in 3.5% of cases. In addition, CEA indicators correlate with the stages of the tumor process (the more advanced the stage, the higher the CEA).

The grade of tumor cell differentiation (G) is another useful preoperative parameter that can aid in the biological evaluation of colorectal tumors. Currently, four grades of differentiation are recognized: G1 - well-differentiated tumors; G2 - moderately differentiated tumors; G3 - poorly differentiated tumors; G4 - undifferentiated tumors. This classification is based on the analysis of various gastopathological criteria of tumor cells, such as mitotic index, loss of nuclear polarity, nuclear size, hyperchromatism, glandular and cellular atypia, pleomorphism, and invasiveness. About 20% of rectal tumors are well differentiated, 50% are moderately differentiated, and the remaining 30% are poorly differentiated and undifferentiated. It is emphasized that the degree of differentiation clearly correlates with the presence of metastases in the lymph nodes: indeed, metastases in the lymph nodes are observed in G1, G2 and G3-4 in 25, 50 and 80% of cases, respectively.

The study of flow cytometry histograms of colorectal cancer DNA was compared with tumor size, Duke staging, differentiation grade, preoperative CEA level, and patient survival. When studying DNA diploidy in tumors, the prognosis was statistically worse (p = 0.017) with non-diploid DNA compared with diploid DNA, but the worst prognosis was with tetraploid DNA in tumor cells.

Colon cancer screening

Ways and means of early detection of colon cancer and precancerous diseases are still being sought. The expediency of conducting preventive examinations to detect colon diseases is beyond doubt. However, during examinations, the doctor faces a number of difficulties, primarily the reluctance of a practically healthy person to undergo such procedures as rectoscopy, colonoscopy, etc. That is why it is necessary to develop an organizationally easy-to-implement study. At present, such a test is the fecal occult blood test, which was developed in the early 1960s, and since 1977 has been introduced into widespread clinical practice. This method is based on the well-known guaiacol reaction, modernized by Gregor and called the "hemoccult test".

Today, the hemoccult test is the only screening test for colorectal cancer. It is easy to perform and does not require large expenses. This test is widely used in Europe and the USA, as well as in Southeast Asia and Japan. The hemoccult test helps reduce mortality from colorectal cancer by 14-18%.

Colorectal cancer screening should be performed at least once every two years. If the result is positive, a colonoscopy should be performed on each patient.

Since colon cancer develops mainly from polyps, which can also be detected using the hemoccult test, this method can be considered not only as a way to detect cancer early, but also as a way to prevent it. Detection and treatment of colon polyps is an important preventive measure in reducing rectal and colon cancer.

Another screening test for early detection of colorectal cancer has been proposed in the United States. The method is based on the analysis of mucus taken from the rectum. Mucus stained with the Schiff reagent changes its color in the presence of neoplasia in the colon. The method is simple, cheap, fast and does not give a large percentage of false positive and false negative results. The test comes with a kit for its implementation.

Recently, significant interest has been generated by developments by domestic and foreign researchers that allow genetic screening of colorectal cancer. Colorectal cancer cells are excreted with feces, providing a potential opportunity for early detection of the disease using a non-invasive method.

The method is based on the detection of mutant genes TP53, BAT26, K-KA5 in DNA of colorectal tumor cells isolated from feces and amplified using polymerase chain reaction (PCR). This method is in the development stage, but upon achieving acceptable sensitivity and specificity, as well as cost, its prospects are very promising.

Recently, a coprological study of tumor M2-pyruvate kinase has been proposed for colorectal cancer screening. This method allows detecting non-bleeding tumors in the colon, and is highly sensitive and specific. The results of using this technique have not yet been described in Russian literature.

To improve the quality of diagnostics, it is necessary to introduce screening examinations into clinical practice with subsequent use of radiological and endoscopic methods, as well as to conduct further scientific development of criteria that allow the formation of a high-risk group.

[ 47 ], [ 48 ], [ 49 ], [ 50 ], [ 51 ]

Differential diagnosis

Differential diagnostics of colon cancer is carried out with tuberculous lesions of the intestine, benign tumors, polyps and sarcoma of the colon. Sometimes, when palpating the colon, a round formation is detected, which an inexperienced doctor often immediately evaluates as a cancerous tumor, however, it is often just an accumulation of feces in the intestine, and the next day the previously palpated "tumor" is not determined. If the tumor formation is palpated in the right iliac region, it may be an appendicular infiltrate.

Treatment colon cancer

Colon cancer is treated surgically. In chemotherapy, 5-fluorouracil and fluorofur are prescribed in inoperable cases; the first drug gives the best result in most cases. However, the effect of chemotherapy is short-lived and is observed in only half of patients with colon cancer.

In some cases, radiation therapy is performed before or after surgery. However, the effectiveness of this treatment is low. In advanced cases, when it is impossible to perform a radical operation (resection of the affected area) and intestinal patency is impaired, a palliative operation is performed, which consists of turning off the affected area of the intestine by applying a bypass anastomosis or, in the case of rectal cancer, by applying anus praeternaturalis. Symptomatic drug therapy in advanced cases is reduced to prescribing antispasmodics, and in the case of very severe pain - narcotic analgesics. In case of bleeding and hypochromic anemia, hemostatic agents, iron preparations, and blood transfusions are effective.

Treatment for colon cancer involves surgery.

Before surgery on the colon, patients need preoperative preparation aimed at cleansing the intestine. In recent years, fortran dissolved in 3 liters of water has been used orally for bowel preparation. Orthograde bowel lavage is also used by introducing 6-8 liters of isotonic solution through a tube installed in the duodenum. Less commonly, a slag-free diet and cleansing enemas are used.

Surgical treatment of colon cancer depends on the location of the tumor, the presence or absence of complications and metastases, and the general condition of the patient. In the absence of complications (perforation, obstruction) and metastases, radical operations are performed - removal of the affected parts of the intestine together with the mesentery and regional lymph nodes.

In case of cancer of the right half of the colon, a right-sided hemicolectomy is performed (the terminal ileum of 15-20 cm in length, the cecum, the ascending and right half of the transverse colon are removed), completing the operation with the imposition of an end-to-side or side-to-side ileotransverse anastomosis. In case of cancer of the middle third of the transverse colon, a resection of the transverse colon is performed, completing it with an end-to-end colocoloanastomosis. In case of cancer of the left half of the colon, a left-sided hemicolectomy is performed (a part of the transverse colon, the descending colon and a part of the sigmoid colon are removed) with the imposition of a transverse sigmoidostomy. In case of cancer of the sigmoid colon, a resection of the intestine with the removal of regional lymph nodes is performed.

In the presence of complications such as intestinal obstruction, perforation or inflammation with the development of peritonitis, two-stage resections of the colon with external diversion of intestinal contents are performed. The most common of these operations is the Hartmann operation. The operation is proposed for the treatment of sigmoid colon cancer and the recto-sigmoid section. Resection of the intestine is performed with tight suturing of the distal section and bringing the proximal section out as a colostomy. Restoration of intestinal continuity is performed after a certain time in the absence of relapse or metastases.

In the presence of an inoperable tumor or distant metastases, palliative surgeries are performed to prevent intestinal obstruction: palliative resections, the imposition of a bypass ileotransverse anastomosis, transverse sigmoid anastomosis, or a colostomy.

Chemotherapy after surgery for colon cancer is prescribed to patients when the tumor has invaded the entire thickness of the intestinal wall and when there are metastases in the regional lymph nodes. At an advanced stage of the disease, approaches to chemotherapy depend on the general condition of the patient and are individual. In this situation, it is aimed at improving the quality of life.

The main method of treating colorectal cancer remains surgical. Radical operations for rectal cancer are aimed at removing the tumor and regional lymph nodes.

Modern principles of surgical treatment of colorectal cancer are:

• removal of the affected part of the intestine in a single block with the tissue and vascular-nerve bundle, with high ligation of the vessels, retreating 10 cm above the tumor and 5 cm below the tumor for the colon and at least 2 cm for the rectum;
• total mesorectumectomy (removal of the rectum with surrounding tissue, vascular-nerve structures and lymph nodes limited by visceral fascia) should be performed acutely;
• to ensure a lateral resection margin for rectal cancer, it is necessary to remove the mesorectum without damaging the autonomic nerves of the pelvis (hypogastric, sacral nerves and pelvic plexus). Removal of tumors of the middle and lower ampullar region of the rectum should be accompanied by total mesorectumectomy, whereas for cancer of the upper ampullar region, it is sufficient to limit the resection of the mesorectum to 5 cm distal to the tumor;
• In case of localized cancer of the distal rectum (T1-2 N0M0), located above 2 cm from the dentate line, it is permissible to perform sphincter-preserving interventions with mandatory morphological control of the resection edges.

The most common procedures used for rectal cancer are abdominoperineal extirpation of the rectum, anterior resection of the rectum, abdominoanal resection of the rectum with lowering of the sigmoid colon (or transverse colon), and Hartmann's operation (obstructive resection).

The choice of radical surgery for rectal cancer is determined mainly by the distance of the tumor from the anus. If the tumor is located less than 6-7 cm from the anus, abdominoperineal extirpation of the rectum is used. If the tumor is located more than 6-7 cm from the anus, sphincter-preserving surgeries (abdominoperineal resection with lowering of the sigmoid colon) can be performed.

If the tumor is located higher than 10-12 cm from the anus, anterior resection of the rectum is advisable. Transabdominal resection of the rectum and sigmoid colon with the imposition of a single-barrel colostomy (Hartmann's operation, obstructive resection) is performed if the tumor is located higher than 10-12 cm from the anus and it is impossible to perform anterior resection of the rectum for one reason or another (for example, during an emergency operation performed due to intestinal obstruction, when the intervention is performed on an unprepared intestine).

Palliative surgeries are performed when severe symptoms of intestinal obstruction develop and radical surgery is impossible. They involve the application of a double-barreled colostomy or sigmoid colostomy on the anterior abdominal wall in the left iliac region.

Despite numerous doubts about the justification of using laparoscopic technologies in the treatment of malignant diseases, minimally invasive methods are gradually being introduced in interventions for colon cancer. It should be noted that at present, the specialized literature contains data on quite significant experience in performing laparoscopic anterior resections for cancer.

Preliminary experience shows that the use of laparoscopically assisted interventions on the rectum for malignant neoplasms is justified and appropriate. The use of laparoscopic technologies leads to a decrease in the number of postoperative complications, a decrease in the severity of pain syndrome and a decrease in the need for narcotic analgesics. Laparoscopic technologies allow performing interventions on the rectum in compliance with all oncological principles, ensuring the necessary boundaries and volumes of resections. Some negative impact on the expected benefits of laparoscopic operations is observed when it is necessary to perform minilaparotomic incisions to remove the resected colon.

To make a final judgment about the place and role of laparoscopic interventions in rectal cancer surgery, it is necessary to wait for the results of currently conducted multicenter prospective randomized comparative studies.

In stage III distal rectal cancer, i.e. when the tumor has invaded all layers of the intestinal wall and grown into fatty tissue, as well as in the case of metastatic lesions of regional lymph nodes, combined treatment methods are used to improve long-term results. This is due to the fact that locoregional relapses after surgical treatment of rectal cancer are 20-40%.

Tumor extension beyond the visceral fascia of the rectum is an indication for preoperative radiation therapy. In case of regional lymph node involvement, preoperative radiation therapy should be supplemented by postoperative chemo- or radiation therapy.

Currently, scientists are searching for methods that allow increasing the radiation dose delivered to the tumor and its regional metastasis zones while simultaneously protecting healthy tissues. Hypoxia radiotherapy is such a method. It has been established that under hypoxic conditions, the body becomes more resistant to radiation aggression. Therefore, a hypoxic gas mixture containing 91% nitrogen and 9% oxygen (HGS-9) began to be used as a radioprotector.

In general, preoperative intensive radiation therapy using a hypoxic gas mixture (HGM-9) allows for a 25% increase in the total focal dose delivered to the tumor and areas of possible regional metastasis, without increasing the number and severity of general radiation reactions.

Increasing radiation doses to a total dose of 25 Gy improves five-year survival rates of patients compared to radical surgical treatment by 16.4% (N. N. Blokhin Russian Cancer Research Center).

Irradiation is used to affect the tumor and the routes of its direct spread, i.e. the zones of regional lymphogenous metastasis, and chemotherapy helps to destroy subclinical metastases.

The Mayo Clinic regimen, a combination of 5-fluorouracil and leucovarine, has become widely used worldwide for colorectal cancer chemotherapy. This combination significantly increases patient survival and is used most often as a standard of care.

The emergence of new cytostatics (taxanes, gemcitabine, topomerase I inhibitors, tirapazamine, UFT, etc.) opens up prospects for research on the optimization of chemoradiation therapy.

Forecast

Five-year survival depends primarily on the stage of the disease, histological structure and growth pattern of the tumor. The prognosis is more favorable if the operation is performed at stages I-II of the disease, with an exophytic tumor, especially if it has a high degree of differentiation. The prognosis is less favorable in young patients, especially with anal cancer.

The five-year survival rate of patients with rectal cancer with regional metastases is 42.7%, while in the absence of metastases it is 70.8%.

[ 52 ], [ 53 ], [ 54 ]