Differential benefit of capecitabine-based chemotherapy among TNBC subtypes in the context of the CBCSG010 study.

528 Background: Our previous study classified TNBCs into four mRNA subtypes, provided additional insights into TNBC heterogeneity and potential therapeutic options. Then we conducted a phase Ib/II subtyping-based and genomic biomarker-guided umbrella trial (FUTURE, NCT03805399 ), demonstrated the clinical benefit of subtyping-based targeted therapy for refractory metastatic TNBC. Here, we further evaluate the prognosis and predictive value of molecular classification in early TNBC in CBCSG010 trial (NCT01642771), which is a prospective, randomized phase III trial confirmed adding capecitabine to anthracycline-taxane-based adjuvant chemotherapy significantly improved survival in TNBC. Methods: Tumor tissues and pathological sections were retrospectively collected. Immunohistochemical (IHC) staining and hematoxylin and eosin (HE) staining were performed on paraffin-embedded sections to conduct TNBC IHC subtype staining. RNA-sequencing were performed to characterize the intrinsic molecular features of TNBC microenvironment. Results: 585 patients enrolled in the CBCSG010 trial, 450 patients had pathological sections, among which 207 patients achieved successfully stained sections. PDL1, CD8 and stromal tumor infiltrating lymphocytes (sTILs) were chosen for identified TNBC Immune enriched phenotype. Patients with ≥20% positive tumor cell proportion score (TPS) of PDL1, ≥10% positive cells of CD8, and ≥10% positive sTILs were significantly associated with better 5y-DFS (disease-free survival). Among Immune enriched TNBC, kaplan-Meier curves showed that DFS rates were 96.4% and 73.7% in the capecitabine and control groups. Transcriptome data was used to picture the immune microenvironment landscape, showed that “immune-hot” patients (immune cells or immune genes enriched) were more likely to benefit from capecitabine treatment. Conclusions: TNBC subtypes is significantly associated with DFS, with Immune enriched phenotype achieving the best outcome, and “immune-hot” patients are more likely to benefit from adjuvant capecitabine. Designing future clinical trials adding immunotherapy in adjuvant treatment of TNBC might base on molecular features.