Colorectal cancer

Colorectal cancer is common enough. Symptoms of colorectal cancer include blood in the stool or changes in intestinal delivery. Screening includes the study of a stool for concealed blood. The diagnosis is made with a colonoscopy. Treatment of colorectal cancer consists of resection and chemotherapy in case of involvement of lymph nodes.

In the United States, approximately 130,000 cases and 57,000 deaths are reported each year for colorectal cancer. In the West, the annual registration of colon and rectum cancer reveals more new cases than cancer of any other localization than lung cancer. The incidence begins to rise at 40 years and its peak reaches 60-75 years. In general, 70% is the lesion of the rectum and sigmoid colon and 95% of adenocarcinoma. Colon cancer is more common in women; rectal cancer is more common in men. Synchronous cancers (more than one) are observed in 5% of patients.

[1], [2], [3], [4], [5], [6]

What causes colorectal cancer?

Colorectal cancer most often develops as a degeneration of adenomatous polyps. Approximately 80% of cases are sporadic and 20% have a hereditary component. Predisposing factors include chronic ulcerative and granulomatous colitis; the risk of cancer increases with the duration of the course of these diseases.

Populations with a high incidence of colorectal cancer use foods low in fiber and in large quantities animal protein, fat and refined carbohydrates. Carcinogens can be ingested with food, but more likely they are produced by the microflora from nutritional substances, bile or intestinal secretions. The exact mechanism is unknown.

Colorectal cancer spreads directly through the intestinal wall, hematogenously, by regional metastasis to the lymph nodes, perineurally and by intraluminal metastasis.

Symptoms of colorectal cancer

Colorectal adenocarcinoma grows slowly, and passes a fairly large interval of time before the first signs can appear. Symptoms depend on the location of the tumor, type, extent of spread and complications.

The right side of the large intestine has a large diameter, a thin wall and its contents are liquid, so obstruction develops in the last place. Bleeding is usually hidden. Fatigue and weakness caused by severe anemia may be the only complaints. Tumors sometimes become large enough to allow them to be palpated through the abdominal wall before other symptoms appear.

The left part of the large intestine has a smaller lumen, the feces have a semi-solid consistency, and the tumor tends to circularly narrow the lumen of the gut, causing transient constipation and frequent stools or diarrhea. Clinical symptoms of colorectal cancer are partial obturation with colic pains in the abdomen or intestinal obstruction. The chair can be ribbon-shaped and mixed with blood. Some patients develop perforation symptoms, usually with limited (local pain and tension) or less often with diffuse peritonitis.

With rectal cancer, the main symptom is bleeding during defecation. Whenever there is rectal bleeding, even if there is severe hemorrhoids or diverticular disease in an anamnesis, concomitant cancer should be eliminated. There may be tenesmus and sensations of incomplete bowel movement. Pain appears when peri-rectal tissues are involved.

Some patients may initially have symptoms and signs of metastatic damage (eg, hepatomegaly, ascites, enlargement of supraclavicular lymph nodes).

Screening and diagnosis of colorectal cancer

Screening

Early diagnosis of colorectal cancer depends on routine examination, especially the study of feces for latent blood. The cancer detected by this study is usually in an earlier stage and, consequently, treatment can be more effective. In patients older than 50 years of moderate risk, a study on occult blood should be performed annually, and sigmoidoscopy with a flexible endoscope every 5 years. Some authors recommend colonoscopy every 10 years instead of sigmoidoscopy. Colonoscopy every 3 years can be more effective. Screening examination of patients with risk factors (eg, ulcerative colitis) is discussed with the corresponding diseases.

Diagnostics

Patients with positive tests for occult blood require colonoscopy, as well as patients with pathological changes revealed by irrigoscopy or sigmoidoscopy. All pathological changes should be completely removed for histological examination. If the formation is on a broad base or can not be removed during a colonoscopy, indications for surgical treatment should be strongly considered.

Irrigoscopy, especially with double contrast, can reveal many pathological changes, but it is not as informative as a colonoscopy, therefore irrigoscopy is less preferable as an initial diagnostic study.

Once the cancer is diagnosed, patients need to perform CT of the abdominal cavity, chest X-ray and routine laboratory tests to identify metastatic lesions, anemia and homeostasis assessment.

An increase in the levels of cancer embryonic antigen of serum (CEAg) is observed in 70% of patients with colorectal cancer, but this test is not specific and therefore not recommended for screening. However, if the level of CEAg is high before surgery and low after removal of the colon tumor, monitoring of CEAg may be useful for early diagnosis of relapse. CA 199 and CA 125 are other tumor markers that can also be used.

[7], [8], [9], [10], [11], [12]

Treatment of colorectal cancer

Surgical treatment of colorectal cancer

Surgical treatment of colorectal cancer can be shown 70% of patients without signs of metastatic disease. Surgical treatment consists of a wide resection of the tumor and its regional lymphatic outflow with anastomosing the ends of the intestine. If there is a 5 cm unchanged bowel area between the tumor lesion and the anal edge, an abdominal-perineal resection with a constant colostomy is performed.

Resection of a limited number (1-3) of liver metastases is recommended in non-depleted patients as a subsequent selection procedure. The criteria are as follows: the primary tumor was resected, the liver metastasis is in one lobe of the liver and there are no extrahepatic metastases. Only a small number of patients with liver metastases fall into these criteria, but survival after surgery for 5 years is 25%.

Stages of colorectal cancer ¹

Stage	Tumor (maximum invasion)	Metastases in regional lymph nodes	Remote metastases
0	Tis	N0	M0
I	T1 or T2	N0	M0
II	TK	N0	M0
III	Any Tili T4	Any N or N0
IV	Any T	Any N	M1

¹ TNM classification: Tis - carcinoma in situ; T1 - submucosa; T2 - actually muscle; T3 - penetrates through all layers (for rectal cancer, including perirectal tissue); T4 - adjacent organs or peritoneum.

N0 is none; N1 - 1-3 regional nodes; N2 -> 4 regional nodes; N3 - apical nodes or in the course of vessels; M0 - no; M1 - are available.

Ancillary treatment of colorectal cancer

Chemotherapy (usually 5-fluorouracil and leucovorin) increases survival by 10-30% in patients with colon cancer with lymph node involvement. Effective combined radiotherapy and chemotherapy in patients with rectal cancer and 1-4 lymph nodes; If the lesion is detected more than 4 knots, the combined methods are less effective. Preoperative radiotherapy and chemotherapy can improve the resectability of rectal cancer and reduce metastasis in the lymph nodes.

[13], [14], [15], [16]

Subsequent screening

In the postoperative period, a colonoscopy should be performed annually for 5 years, and then every 3 years, if polyps or tumors are not detected. If preoperative colonoscopy was incomplete because of obturation cancer, complete colonoscopy should be performed 3 months after surgical treatment.

An additional screening test for relapse should include anamnesis, physical examination and laboratory tests ( general blood test, functional liver tests) every 3 months for 3 years and then every 6 months for 2 years. Instrumental studies (CT or MRI) are often recommended for 1 year, but their usefulness is questionable in the absence of abnormalities in screening or in blood tests.

Palliative treatment of colorectal cancer

If surgical treatment is not possible or there is a high risk of surgery on the part of the patient, palliative treatment of colorectal cancer is indicated (eg, reduction in obturation or resection of the perforation zone); survival is on average 6 months. Some tumors that cause obturation can be reduced in volume by endoscopic laser coagulation, electrocoagulation or stenting. Chemotherapy can reduce swelling and prolong life for several months.

Other drugs such as irinotecan (camptosar), oxaliplatin, levamisole, methotrexate, formyltetrahydrofolic acid, celecoxib, thalidomide and capecitabine (a precursor of 5-fluorouracil) have been investigated. However, there are no most effective regimens for metastatic colorectal cancer. Chemotherapy for advanced colon cancer should be performed by an experienced chemotherapist who has access to drug research.

If metastasis is limited to the liver, it is more effective than systemic chemotherapy in outpatient settings to intra-arterial intrahepatic administration of floxuridine or radioactive microspheres using an implantable subcutaneous or external pump fixed to the waist. In the case of extrahepatic metastasis, intrahepatic arterial chemotherapy does not assume any advantage over systemic chemotherapy.

What is the prognosis of colorectal cancer?

Colorectal cancer has a different prognosis. It depends on the stage. The 10-year survival rate for cancer confined to the mucosa is approaching 90%; when germinating through the wall of the intestine - 70-80%; at a lesion of lymph nodes - 30-50%; with metastasis - less than 20%.