Prognostic and predictive impact of gene expression in node-positive early breast cancer patients receiving dose-dense versus standard-dose adjuvant chemotherapy.

The utility of multigene expression assays in advanced (≥ 4 positive lymph nodes) early breast cancer (EBC) is limited. We conducted exploratory transcriptomic analysis of 758 genes (Breast Cancer 360 panel, nCounter® platform; NanoString) in primary tumor samples collected during a phase 3 trial comparing adjuvant taxane-containing dose-dense chemotherapy (ddCTX) versus standard-dosed chemotherapy (stCTX) in resected EBC with ≥ 4 positive lymph nodes. Prognostic and predictive associations with disease-free survival (DFS) and overall survival (OS) were evaluated by Cox regression with false discovery rate (FDR) adjustment. Data were available from tumor samples of 141/226 patients (median follow-up: 14 years). Several genes/signatures, including immune markers, showed prognostic relevance in unadjusted analyses. Of these, two remained significant after multiplicity adjustment: a positive effect on DFS of programmed cell death 1 ligand-2 (PD-L2) in the ddCTX arm (univariate HR: 0.53, FDR-adjusted P = 0.036) and a negative effect on OS of HER2-enriched (HER2-E) signature in the stCTX arm (univariate HR: 5.40, FDR-adjusted P = 0.036). Predictive analyses showed greater DFS benefit of ddCTX in tumors with high antigen processing machinery (APM) expression (multivariate interaction P = 0.024). Multigene expression assays have a prognostic and predictive potential in advanced EBC, and further investigation is warranted in order to identify candidates for de-escalated treatment. In addition, intrinsic subtype and immune gene expression have predictive potential.