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Analyzes for breast cancer
Last reviewed: 23.04.2024
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Diagnosis of cancer can not be imagined without testing, and tests for breast cancer are included in the list of mandatory studies performed after mammography.
But the treatment strategy is determined not by the analysis of blood in breast cancer, but by immunohistochemical analysis of the tumor biopsy material.
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Blood test for breast cancer
What information about the patient's health gives the doctor a general blood test for breast cancer? This is objective data for:
- the number of leukocytes in the blood and their composition (leukocyte formula);
- color index of blood (relative hemoglobin content in one erythrocyte);
- the number of platelets and granulocytes;
- the volume of erythrocytes (hematocrit), the rate of their deposition (ESR) and the level of young erythrocytes (reticulocytes);
- hemoglobin level (HGB).
As experts note, the general analysis of blood in breast cancer has no diagnostic value for assessing possible oncology in the early stages, but gives an idea of the functional state of the bone marrow.
Biochemical analysis of blood in breast cancer will show the level of electrolytes (potassium and calcium) and enzymes (alkaline phosphatase), which can be abnormal in the metastasis of tumors. However, a change in their levels is often observed in many pathologies, and therefore the diagnosis of breast cancer requires other tests.
Analysis for cancer markers of breast cancer
To date, the diagnostic standard in oncology is the study of venous blood for the presence and level of proteins produced by cancer cells, perceived by the immune system as antigens. This is the analysis for cancer markers of breast cancer (CA or tumor marker).
The CA 15-3 marker, according to the diagnostic rules of the International Association of Oncologists, does not apply to specific antigens for breast cancer, as its blood level is also elevated in patients with malignant neoplasms in the lungs, pancreas, liver, bladder, ovaries and uterus.
As practice shows, it can hardly be considered specific for breast cancer and the cancer marker CA 27.29, since an increase in its content in the blood plasma can be noted with fibromatous changes in the breast, inflammation of the endometrium and ovarian cyst.
The analysis for cancer markers of breast cancer may include a CEA-carcinoembryonic antigen test (carcinoembryonic antigen). But it is determined by no more than 30% of cases of breast cancer. Moreover, its content in the serum can grow with chronic obstructive pulmonary disease, hypothyroidism, ulcerative colitis, granulomatous enteritis (Crohn's disease), pancreatitis and liver cirrhosis. So this blood test for breast cancer is not reliable both for diagnosis and as a screening test for early detection of cancer.
Immunohistochemical analysis of breast cancer
IHC test (ImmunoHistoChemistry) - Immunohistochemical analysis of breast cancer - is carried out by examining a tumor tissue sample that is obtained by biopsy or after removal of the tumor in the chest.
Her2 analysis in breast cancer is the definition of the human epidermal growth factor receptor, that is, the tyrosine kinase receptor of the epidermal growth factor (second type), which is found on the membranes of cells in the tumor tissue. If there is an increased expression of her2 receptors (result of the 3+ assay), then the IHC test shows "her2 positive": the malignant formation is in the process of growth. If the index is from 0 to 1+, then her2 is negative; the 2+ indicator is considered borderline.
There is also an immunohistochemical analysis of breast cancer (IHC test) for the expression of breast tumor cells by the receptors for estrogen (ERS) and progesterone (PRS). When the number of such receptors is large (exponent 3), then the growth of cancer cells is "fueled" by hormones. The indicator 0 - receptors of hormones is not present (that is a tumor of a hormone-receptor-negative); 1 - a small amount of ERS and PRS; 2 - average.
The presence of estrogen receptors (ERS) is a weak prognostic marker of the clinical outcome of the disease, but it is of great importance for the purpose of hormone therapy.
Genetic analysis of breast cancer
It has been established that in tumor cells the synthesis of receptors of epidermal growth factor (her2) occurs with the increased activity of genes. In the cells of the bioptate, the analysis of fish in breast cancer, or more precisely, the FISH test (Fluorescence In Situ Hybridization), reveals their activity.
Fluorescent hybridization at a given site (in situ) is a cytogenetic method using the principle of fluorescent labeling of probes (short DNA sequences) and studying them with fluorescence microscopy. The study allows to detect the presence of specific DNA sequences on chromosomes and to establish their localization, as well as specific RNA targets in cells of tumor tissues.
This test visualizes specific genetic structures in the cells of a cancerous tissue. The more additional copies of the her2 gene have cells, the more these cells have her2 receptors; receptors accept signals that stimulate the growth of atypical cells.
However, oncologists note significant discrepancies between the results of immunohistochemical analysis of breast cancer (IHC test) and FISH-test. Although the analysis of fish in breast cancer can be used for species identification of tumors.
The Oncotype DX test examines 21 genes to assess the risk of recurrence of estrogen-dependent cancers of stage I or II, and also gives grounds for deciding whether to use chemotherapy in addition to hormonal.
Genetic analysis of the predisposition to breast cancer is a study of BRCA1 genes (on the 17th chromosome) and BRCA 2 (on the 13th chromosome) aimed at revealing their hereditarily caused anomalies.
Analysis of the risk of developing breast cancer (for the mutation of the BRCA1 and BRCA2 genes) is performed on blood or saliva samples. It can give several possible results: positive, negative or indeterminate. But even a positive result of this analysis can not give information about whether a person will get cancer and when. For example, some women with a positive result remain healthy.
By the way, there is no evidence of the effectiveness of bilateral preventive mastectomy in reducing the likelihood of breast cancer, which revealed an analysis of the risk of developing breast cancer or a family history of cancer.
Interpretation of blood test for breast cancer
An extremely important stage of laboratory research is the interpretation and interpretation of the results of the analyzes. The principle on which the decoding of the blood test in breast cancer is based is to determine the level of oncomarkers and compare it with the normative indices.
For example, the normal level of the cancer marker CA 15-3 is recognized as below 30 U / ml, and oncology may indicate a level above 31 U / ml. Given the nonspecificity of this oncomarker, this test is used to control the disease during treatment. The norm of the tumor marker CA 125 is 0-35 units / ml, CA 27.29 - below 38 units / ml. In general, the levels of cancer markers more than 100 units / ml mean the explicit presence of oncology.
It should be borne in mind that in a third of patients within 30-90 days after treatment, the results of the analysis for serum marker cancer markers CA 27.29 are elevated, so for the second course of chemotherapy, this analysis should be done only 2-3 months after treatment.
And for carcinoembryonic antigen CEA, the normal level for non-smokers is less than 2.5 ng / ml, and for smokers - up to 5 ng / ml. As a rule, CEA> 100 indicates metastatic cancer (stage III-IV) or relapse after cancer treatment.