Kaplan-Meier curves for time to recurrence (TTR) in the high-risk subgroup of the validation set (n = 394). (a) Kaplan-Meier curves for TTR according to CD8+ T-lymphocyte fraction in patients with high-risk stage ΙΙΙ colorectal cancer (CRC). 5-year TTR: 62% (95% CI 55–70) for the patients with high CD8+ T-lymphocyte fraction versus 51% (95% CI 45–59) for the patients with low CD8+ T-lymphocyte fraction (Mantel-Cox log-rank test, P = 0.028). (b) Kaplan-Meier curves for TTR according to stroma fraction. 5-year TTR: 59% (95% CI 54–65) for the patients with low stroma fraction versus 41% (95% CI 30–55) for the patients with high stroma fraction (Mantel-Cox log-rank test, P = 0.002). (c) Kaplan-Meier curves for TTR according to combined CD8+ T-lymphocyte fraction/stroma fraction. 5-year TTR: 64% (95% CI 56–73) for the patients with high CD8+ T-lymphocyte fraction/low stroma fraction, 55% (95% CI 49–63) for the patients with combined low CD8+ T-lymphocyte fraction/low stroma fraction or combined high CD8+ T-lymphocyte fraction/high stroma fraction, and 29% (95% CI 17–50) for the patients with low CD8+ T-lymphocyte fraction/ high stroma fraction (Mantel-Cox log-rank test, P < 0.001). High-risk stage ΙΙΙ CRC: pathological tumor stage (pT) 3 pathological lymph node stage (pN) 1 with either lymphovascular invasion (L+) or venous vascular invasion (V+); pT4; or pN2. HR, hazard risk; CI, confidence interval.