Tailoring Escalation Adjuvant Therapy for Early-Stage Triple-Negative Breast Cancer in the CBCSG010 Clinical Trial Biomarker Analysis.

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Triple-negative breast cancer (TNBC) is a highly heterogeneous disease. The CBCSG010 trial is a prospective and multicenter phase III clinical trial confirming that adding adjuvant capecitabine significantly improved the 5-year disease-free survival (DFS) rate in patients with TNBC by 5.9%. In this study, we attempted to identify the specific population that benefited from adjuvant therapy. In this retrospective exploratory analysis, we performed RNA sequencing of tumor tissues from patients with TNBC in the CBCSG010 clinical trial. A single-sample gene set enrichment analysis algorithm and survival analysis were performed to characterize the intrinsic molecular features of the TNBC microenvironment and assess the associations between immune-related gene expression levels or immune cell counts with capecitabine treatment efficacy. Additionally, we performed immunohistochemical staining of 2 markers, PD-L1 and CD8, and hematoxylin-eosin staining of stromal tumor-infiltrating lymphocytes (sTILs) on formalin-fixed, paraffin-embedded specimens to validate findings from bioinformatics analyses. We found that patients with TNBC with high immune-infiltration treated with capecitabine were more likely to have a better prognosis. We used a cutoff of ≥25 combined positive score (CPS) of PD-L1, ≥10% positive sTILs, and ≥10% positive cells of CD8 to define the "immune-hot" patients. Among immune-hot patients, Kaplan-Meier curves showed that 5-year DFS rates were 96.9% and 79.4% in the capecitabine and control groups, respectively (hazard ratio, 0.13; 95% CI, 0.03-0.52; P=.049 in favor of capecitabine). In the capecitabine group, the 5-year DFS rate was higher for immune-hot patients than for immune-cold patients (96.9% vs 76.4%; hazard ratio, 0.11; 95% CI, 0.04-0.29; P=.028). Our study suggested that immune-hot patients with TNBC are more likely to benefit from adjuvant capecitabine, and that combining immunotherapy with chemotherapy may be expected to be more effective in immune-hot patients.