CD8(+) T-cell Density Is an Independent Predictor of Survival and Response to Adjuvant Chemotherapy in Stage III Colon Cancer

We assessed CD8(+) T-cell density in 351 resected stage II to III colon cancers from 2011 to 2015 and correlated the findings with disease-free survival and survival effect of adjuvant chemotherapy. Most tumors (70%) had high/intermediate CD8(+) T-cell density, and this was significantly associated with mismatch repair deficiency compared with tumors with low CD8(+) T-cell density (28% vs. 13%, P=0.003). Fewer tumors with high/intermediate CD8(+) T-cell density had adverse histologic features compared with tumors with low CD8(+) T-cell density including high tumor budding (16% vs. 27%) and venous (22% vs. 35%), lymphatic (54% vs. 65%), and perineural (23% vs. 33%) invasion (all with P<0.05). In the stage III cohort, high/intermediate CD8(+) T-cell density was an independent predictor of disease-free survival on multivariate analysis (hazard ratio: 0.39, 0.21 to 0.71 95% CI, P=0.002). For stage III patients with high/intermediate CD8(+) T-cell density, adjuvant chemotherapy was significantly associated with improved disease-free survival (hazard ratio: 0.28, 0.11 to 0.74 95% CI, P=0.01) whereas stage III patients with low CD8(+) T-cell density did not have improved survival with adjuvant chemotherapy. In conclusion, in stage III colon cancer, CD8(+) T-cell density is an independent prognostic biomarker for disease-free survival and may help to identify patients who benefit from adjuvant chemotherapy.