Breast cancer biomarker (ER, PR, HER2) changes in the phenotype after neoadjuvant treatment

Abstract

Objective: to study the breast cancer phenotype (ER/PR, FOXA1, HER2, Ki67) and the dynamics of changes in these markers in the tumour before and after neoadjuvant chemotherapy (NAT), compare them with metastases in the regional lymph nodes (LN). Materials and methods. The subject of the study was a group of patients with breast carcinomas receiving NAT according to the TAC and TC regimens, who had metastases in regional LUs in the course of the treatment (urN1,2,3). Results. Patients were divided into three groups. The first group (n = 11, primary tumour and tumour after NAT). The conversion of hormone receptor expression was both upward (37.5%) and downward (62.5%). Expression of HER2 has only changed upward by 36.4%.The second group (n = 32, residual tumour and regional metastases). The conversion of hormonal receptors was reported in 12.5%. Expression of HER2 has changed by 21.87%. In the third group (n = 11, the primary tumour before the onset of NAT and metastasis in LN after treatment). Conversion of ER in 18.2% in the form of a total loss, PR in 54.5%. Expression of HER2 increased by 45.5%. Expression of FOXA1 remained stable in all cases after NAT, where expression of hormonal receptors decreased or disappeared. Conclusions. In the era of personalized therapy and NAT, it is required to conduct a pathomorphological study of the immunohistochemical status of metastases in LN, since the hormone receptor status changes in almost 20% of cases, with the signal pathway for steroid hormone receptors remaining unchanged. The HER-2 oncoprotein expression status changes in almost half of cases when comparing the primary biopsy and metastasis after NAT.