Tumor immunogenomic features determine outcomes in metastatic colorectal cancer patients treated with standard-of-care combinations of bevacizumab and cetuximab.

CALGB/SWOG 80405 was a randomized phase III trial in first-line mCRC patients treated with bevacizumab, cetuximab, or both, plus chemotherapy. We tested the effect of tumor immune features on OS.Primary tumors (N=554) were profiled by RNAseq. Immune signatures of macrophages, lymphocytes, TGF-β, INF-γ, wound healing, and cytotoxicity were measured. CIBERSORTx scores of naive and memory B cells, plasma cells, CD8+ T cells, resting and activated memory CD4+ T cells, M0 and M2 macrophages, and activated mast cells were measured.Increased M2 macrophage score (HR 6.30, 95% CI 3.0-12.15) and TGF-β signature expression (HR 1.35, 95% CI 1.05-1.77) were associated with shorter OS. Increased scores of plasma cells (HR 0.55, 95% CI 0.38-0.87) and activated memory CD4+ T cells (HR 0.34, 95% CI 0.16-0.65) were associated with longer OS. Using optimal cutoffs from these four features, patients were categorized as having either 4, 3, 2, or 0-1 beneficial features associated with longer OS, and the median (95% CI) OS decreased from 42.5 (35.8-47.8), to 31.0 (28.8-34.4), 25.2 (20.6-27.9), and 17.7 (13.5-20.4) months respectively (p-value 3.48e-11).New immune features can be further evaluated to improve patient response. They provide the rationale for more effective immunotherapy strategies.