Prognostic and predictive value of the Immunoscore in stage III colon cancer patients treated with oxaliplatin in the prospective IDEA France PRODIGE-GERCOR cohort study.

•This study provides evidence for the feasibility and reproducibility of the Immunoscore (IS) test.•The IS prognostic value for disease-free survival (DFS) is demonstrated in stage III patients treated with oxaliplatin-based chemotherapy.•A predictive value of the IS (Int + High) for DFS benefit of longer duration of mFOLFOX6 treatment is observed.•Patients with low- and high-risk stage having IS Int + High significantly benefit from 6 months' mFOLFOX6 versus IS Low.