Alteration of PD-L1 (SP142) status after neoadjuvant chemotherapy and its clinical significance in triple-negative breast cancer

Abstract

Purpose The tumor immune microenvironment can change after neoadjuvant chemotherapy (NAC) for triple-negative breast cancer (TNBC). We aimed to investigate the effects of NAC on PD-L1 (SP142) status and its clinical significance in TNBC. Methods Paired samples of biopsy and resection specimens were collected from 182 patients with TNBC before and after NAC. PD-L1 (SP142) expression in immune cells in pre- and post-NAC breast cancer samples and the changes between them were analyzed, along with their relationships with the clinicopathological features and clinical outcomes of the patients. Results Of the 182 patients, 61 (33.5%) achieved pathologic complete response (pCR) after NAC. PD-L1 (SP142) positivity, defined as immune cell staining in ≥ 1% of tumor area, was a predictor for pCR. PD-L1-positive immune cells significantly increased after NAC (2.8% to 5.2% on average) in 109 patients with measurable residual disease. Alteration of PD-L1 status was observed in 24 (22.0%) of the 109 patients with measurable residual tumors after NAC, and all PD-L1 status-converted patients, except one, revealed negative-to-positive conversion. Regarding chemotherapeutic agents, the use of platinum agents was associated with a significant increase in PD-L1-positive immune cells after NAC. In survival analyses, a positive PD-L1 status after NAC and increase of PD-L1-positive immune cells after NAC were associated with better recurrence-free survival of the patients. Conclusion PD-L1 (SP142) status changes after NAC, mostly as a positive conversion. As PD-L1 (SP142) status can convey prognostic and predictive information, it needs to be tested before and after NAC.