Study of the PD-L1 status in breast cancer, by using the SP142 monoclonal antibody, and the prospects for determining treatment policy

Abstract

To investigate the expression of programmed death ligand 1 (PD-L1) in triple-negative and luminal B, HER2-negative breast cancer, by using the SP142 antibody and to assess the association of the PD-L1 status with prognosis for patients. The study was conducted using surgical materials (full sections) obtained from 72 patients. The sections were stained with the SP142 PD-L1 antibody. Differences were found in the detection rates of the PD-L1-positive status in the primary tumor and regional metastasis (primary tumor in 26 (36.1%) cases and metastasis in 18 (47.4%) of the 38 cases). By and large, the PD-L1-positive status was less common in the patients receiving neoadjuvant chemotherapy (25.8% versus 53.7%); however, it should be noted that the PD-L1-positive status was more often detected in those who had a higher residual cancer burden (RCB) (RCB-III versus RCB-II). Considering the findings, it is necessary to clarify the status of not only a primary focus, but also clinically significant metastases, especially if the primary tumor has yielded a negative result. The patients with disease progression who receive standard therapy regimens may have a chance for a good result when using PD-1/PD-L1 blockers. At the same time, the association of the PD-L1 status with RCB may affect the choice of adjuvant treatment policy.