Impact of subdivision of pathological stage I colorectal cancer

Abstract Aim Stage II‐IV colorectal cancers are subdivided according to TNM categories. However, stage I cases are a single category, despite the inclusion of both T1 and T2 cases, which may have different outcomes. The aim of this study was to evaluate the usefulness of subdividing stage I colorectal cancers by T category. Methods From 1984 to 2015, 844 patients with stage I colorectal cancer (T1: 446, T2: 398) underwent colorectal resection with lymph node dissection at three hospitals. The long‐term survival and recurrence rates were compared between T1 and T2. A Cox regression analysis was used to evaluate the risk factors associated with cancer recurrence. Results A comparison of the T1 and T2 groups revealed significant differences in 5‐year overall (95.9% vs 91.4%, P = .008), recurrence‐free (94.8% vs 87.1%, P = .0007), and cancer‐specific survival (97.6% vs 93.6%, P = .004), and in the overall (2.5% vs 6.8%, P = .003), local (0.2% vs 1.5%, P = .04), and lymph node recurrence rates (0.2% vs 1.5%, P = .04). All local and lymph node recurrences were associated with lower rectal cancer, and this difference was significant. The Cox multivariate analysis identified male sex (P = .01, hazard ratio: 4.00, 95% confidence interval: 1.38‐11.55), T2 (P = .02, hazard ratio: 2.98, 95% confidence interval: 1.17‐7.60), and venous invasion (P = .03, hazard ratio: 2.38, 95% confidence interval: 1.12‐5.10) as risk factors for recurrence. Conclusions The subdivision of stage I colorectal cancer according to T category clearly reflected the long‐term outcomes.