Tests for breast cancer

It is impossible to imagine the diagnosis of oncological diseases without taking tests, and tests for breast cancer are included in the list of mandatory studies carried out after mammography.

However, the treatment strategy is determined not by a blood test for breast cancer, but by an immunohistochemical analysis of tumor biopsy material.

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Blood test for breast cancer

What information about the patient's health does a general blood test for breast cancer provide to the doctor? This is objective data on:

• the number of leukocytes in the blood and their composition (leukocyte formula);
• color index of blood (relative hemoglobin content in one red blood cell);
• the number of platelets and granulocytes;
• the volume of red blood cells (hematocrit), their sedimentation rate (ESR) and the level of young red blood cells (reticulocytes);
• hemoglobin level (HGB).

As experts note, a general blood test for breast cancer does not have diagnostic value for assessing possible oncology in the early stages, but it does provide an idea of the functional state of the bone marrow.

A blood chemistry test for breast cancer will show levels of electrolytes (potassium and calcium) and enzymes (alkaline phosphatase), which may be abnormal when tumors metastasize. However, changes in their levels are common in many pathologies, and therefore, breast cancer diagnosis requires other tests.

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Breast cancer tumor marker analysis

Today, the diagnostic standard in oncology is a venous blood test for the presence and level of proteins produced by cancer cells, which are perceived by the immune system as antigens. This is the breast cancer tumor marker test (CA or tumor marker).

The CA 15-3 marker, according to the diagnostic rules of the International Association of Oncologists, does not belong to specific antigens for breast cancer, since its level in the blood is also elevated in patients with malignant neoplasms in the lungs, pancreas, liver, bladder, ovaries and uterus.

As practice shows, the CA 27.29 tumor marker can hardly be considered specific for breast cancer, since an increase in its content in the blood plasma can be observed with fibromatous changes in the breast, with inflammation of the endometrium and ovarian cysts.

Analysis of breast cancer tumor markers may include the CEA test - carcinoembryonic antigen. But it is determined in no more than 30% of breast cancer cases. Moreover, its content in the blood serum may increase 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 either for diagnosis or as a screening test for early detection of cancer.

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Immunohistochemical analysis of breast cancer

IHC test (ImmunoHistoChemistry) – immunohistochemical analysis of breast cancer – is performed when examining a tumor tissue sample, which is obtained by biopsy or after removal of a neoplasm in the breast.

HER2 analysis in breast cancer is the determination of human epidermal growth factor receptor, i.e. tyrosine kinase receptor of epidermal growth factor (type 2), which is located on the membranes of tumor tissue cells. If there is increased expression of HER2 receptors (analysis result 3+), then the IHC test shows "HER2 positive": the malignant tumor is in the process of growth. If the indicator is from 0 to 1+, then HER2 is negative; an indicator of 2+ is considered borderline.

There is also an immunohistochemical analysis of breast cancer (IHC test) for the expression of estrogen receptors (ERS) and progesterone receptors (PRS) by breast tumor cells. When the number of such receptors is large (indicator 3), it means that the growth of cancer cells is “fed” by hormones. Index 0 – no hormone receptors (i.e. the tumor is 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 clinical outcome of the disease, but is of great importance for the prescription of hormonal therapy.

Genetic analysis of breast cancer

It has been established that in tumor cells, the synthesis of epidermal growth factor receptors (her2) occurs with increased gene activity. In biopsy cells, their activity can be detected by FISH analysis in breast cancer, or more precisely, the FISH test (Fluorescence In Situ Hybridization).

Fluorescent hybridization in situ is a cytogenetic method that uses the principle of fluorescent labeling of probes (short DNA sequences) and their study using fluorescent microscopy. The study allows the detection of the presence of specific DNA sequences on chromosomes and the establishment of their localization, as well as specific RNA targets in tumor tissue cells.

This test visualizes specific genetic patterns in cancer cells. The more extra copies of the HER2 gene cells have, the more HER2 receptors those cells have; the receptors receive signals that stimulate the growth of abnormal cells.

However, oncologists note significant discrepancies between the results of immunohistochemical analysis of breast cancer (IHC test) and FISH test. Although FISH analysis in breast cancer can be used for the species identification of tumors.

The Oncotype DX test examines 21 genes to assess the risk of recurrence of estrogen-dependent stage I or II cancer and provides a basis for decisions about the use of chemotherapy in addition to hormonal therapy.

Genetic testing for predisposition to breast cancer involves testing the BRCA1 (on chromosome 17) and BRCA 2 (on chromosome 13) genes to identify hereditary abnormalities.

The breast cancer risk test (for the BRCA1 and BRCA 2 gene mutations) is performed on blood or saliva samples. It can give several possible results: positive, negative, or indeterminate. But even a positive result from this test cannot provide information about whether or when a person will get cancer. For example, some women who have a positive result remain healthy.

By the way, there is no evidence that bilateral prophylactic mastectomy is effective in reducing the risk of breast cancer, as determined by breast cancer risk testing or a family history of cancer.

Decoding blood tests for breast cancer

An extremely important stage of laboratory research is the decoding and interpretation of test results. The principle on which the decoding of a blood test for breast cancer is based is to determine the level of tumor markers and compare it with standard indicators.

For example, a normal level of the CA 15-3 tumor marker is considered to be below 30 U/ml, and a level above 31 U/ml may indicate oncology. Given the non-specificity of this tumor marker, this test is used to monitor the disease during treatment. The norm for the CA 125 tumor marker is 0-35 U/ml, CA 27.29 - below 38 U/ml. In general, tumor marker levels above 100 U/ml indicate the obvious 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 tumor markers CA 27.29 are elevated, so for a repeat course of chemotherapy, this analysis should be done only 2-3 months after treatment.

And for the carcinoembryonic antigen CEA, the normal indicator for non-smokers is a level of less than 2.5 ng/ml, and for smokers - up to 5 ng/ml. As a rule, CEA>100 indicates metastatic cancer (stages III-IV) or a relapse of cancer after therapy.