Estimation of the incidence of molecular disorders in the tumor cells in breast malignant neoplasms by high-throughput sequencing

Objective. To estimate the incidence of molecular disorders in the tumor samples of patients with locally advanced and metastat-ic breast cancer (BC) by high-throughput sequencing (HTS), followed by the assessment of whether the study results can be used to choose treatment policy for individual patients. Material and methods. HTS was used to conduct a molecular genetic study of 76 BC tissue samples, by applying the AVENIO Tumor Tissue Expanded Panel Kit (Roche, USA), that included 77 genes associated with the development of malignant neoplasms. Results. This study identified the most common pathogenic mutations in the TP53, PIK3CA, AKT1, and MET genes in BC, as well as molecular genetic disorders in various genes (BRCA2, PTCH1, ROS1, KIT, PDGFRA, GATA3, APC, PTEN, AR, PDCD1LG2, NTRK1, FLT3, EGFR, FLT1, MSH2, KRAS, RB1, EGFR amplification, PMS2, and CSF1R), which occurred in 1—4% of cases. It should be noted separately that the 2020 clinical guidelines for the diagnosis and treatment of BC in patients with hormone-dependent HER2 BC recommend that PIK3CA gene mutations should be studied to decide whether targeted therapy is given. Our study determined that the frequency of pathogenic mutations in the PIK3CA gene in this patient group was 38.2%. The frequency of mutations in this gene in other (hormone-independent, HER2-positive) subgroups was also quite high (33.3%), which allows one to recommend that PIK3CA gene mutations should be determined for other subtypes of BC. Conclusion. HTS used to examine patients with BC will be able to improve the algorithm for the molecular diagnosis of the dis-ease, to increase the informative value of study results, by obtaining complete information on the studied genes, to reduce the time of diagnosis through a cross-sectional study of several genes at once, to enhance the efficiency of therapy, owing to the timely and accurate identification of genetic markers that are critical to prescribe targeted therapy.