PD-L1 expression and TOP3A mutation as prognostic factors for adjuvant chemotherapy in triple negative breast cancer.

Abstract

541 Background: Triple negative breast cancer (TNBC) is a highly aggressive subtype of breast cancer that is markedly heterogeneous and lacks specific targets. The aim of this study is to explore potential predictors and therapeutic targets based on clinical and genetic characteristics. Methods: 138 patients with triple-negative breast cancer after surgical treatment were 1:1 randomly assigned to the paclitaxel combined with carboplatin (TCb) group or the epirubicin combined with cyclophosphamide sequential paclitaxel (EC-T) adjuvant chemotherapy group. PD-L1 was retrospectively analyzed by surgically resected specimens, and 733 cancer-related genes were detected by NGS. Pathway enrichment analysis was performed using DAVID for functional enrichment genetic alterations. Cox regression models and Kaplan-Meier were used to evaluate disease-free survival (DFS). Results: In this study, there was no significant difference in DFS between the TCb and EC-T groups. 31 (22.5%) of 138 TNBC patients were positive for PD-L1 expression, including 15 (10.9%) patients positive for PD-L1 in tumor cells (TCs) and 29 (21.0%) patients positive for PD-L1 in tumor-infiltrating immune cells (TICs). Patients with positive PD-L1 expression, either in TCs or TICs, achieved better DFS [HR=0.13 (95% CI: 0.02-0.93), p=0.016], the difference was also shown in the EC-T group [HR=0 (95% CI: 0- inf), p=0.037], but not in the TCb group [HR=0 (95% CI: 0.04-2.1), p=0.189]. In addition, we identified 7 patients with mutations in DNA topoisomerase IIIα(TOP3A), a homologous recombination (HR)-related gene, and patients with mutations in this gene had worse DFS than those without mutations [HR=4]. However, there was no statistically significant association between BRCA mutation and response to either therapeutic regimens. Conclusions: In this TNBC patient population, immunohistochemistry (IHC) and NGS analyses identified potential prognostic markers. PD-L1 positive and TOP3A mutation were significantly associated with early triple-negative breast cancer prognosis.