TRIPLE-NEGATIVE BREAST CARCINO-MA: MOLECULAR AND GENETIC CHARACTERISTICS AND PROGNOSTIC FACTORS (LITERATURE

Since the work of Perou about the classification of breast cancer by gene expression profiling has been published, a significant breakthrough in its treatment became evident. Five subgroups of breast cancer were identified: luminal A, luminal B, with amplification of HER2, basal like and normal breast like. Hormonal therapy of luminal subunits of breast cancer (which have oestrogen and progesterone receptors) and target anti-HER2 therapy for breast cancer with HER2 amplification significantly improved survival rates for these groups of patients. However, almost the only option for triple-negative carcinomas, which do not have receptors for oestrogen and progesterone and amplification of HER2, is the use of chemotherapy protocols, which are not always clearly defined. This group includes 10-15% of all breast carcinomas and has the worst survival rates remaining on constant level over the past decades. According to the data of Kyiv City Clinical Oncology Centre, the percentage of triple-negative carcinomas during 2008-2017 was 11.7%. Overall 5-year survival of these patients (who was treated during 2008-2013 years) is 69.6%. The group of triple-negative carcinomas is heterogeneous in terms of its morphological and molecular characteristics. That is why additional classification of triple-negative carcinoma by additional molecular-biological characteristics is necessary. This will allow individualizing the treatment and finding additional prognostic factors. Many attempts were made to classify triple-negative carcinomas. Unified classification has not been created today. However, due to genetic studies, the basal like and luminal androgen-positive variant, which may provide additional information on prognosis or treatment, has been identified. It is also possible and expedient to define these subgroups with the help of surrogate immunohistochemical panels. One of the variants to establish basal like subtype is positive reaction with CK5 / 6 or EGFR in the presence of triple-negative status. In addition, Claudine-low variant was genetically determined, though no influence on prognosis is found for that group of tumors. Triple-negative breast carcinomas are often associated with a breakage of BRCA-1 protein expression, diagnostics of which also provides new treatment options. It has been found that breast carcinomas with “BRCA-ness” are more responsive to neoadjuvant chemotherapy but have worse survival rates and are associated with an increased risk of developing metastases in the brain. Among other prognostic factors, which are explored, PD-L1, topoisomerase IIα (TOP2A) and the tumor suppressor gene p53 should be mentioned. Data about influence of PD-L1 on treatment and prognosis is controversial. TOP2A can help in identifying sensitivity to neoadjuvant therapy, whereas p53 mutation is correlated with lower overall and non-recurrent survival rates. Further studies of triple-negative breast carcinomas are necessary for the purpose of the treatment individualization.