Adverse Pathological Features and Worse Prognosis in Rectal Cancer Compared With Colon Cancer in T1 and T2 Stages

Background and Aim Emerging endoscopic techniques are expanding opportunities for minimally invasive therapy in early colorectal cancers (CRCs). Data regarding the clinicopathological features and outcomes of colon versus rectal cancers in Tis, T1, and T2 stages remain limited. This study evaluates and compares these two entities to clarify their oncologic differences. Methods We retrospectively analyzed patients with pTis‐T2 CRCs treated by endoscopic or surgical resection at a single Japanese center between 2001 and 2022. Tumor location was classified as rectum (Ra, Rb) or colon (cecum to RS). Clinical variables (sex and age), pathological features (tumor size, differentiation, lymphatic invasion [Ly], vascular invasion [V], and tumor budding), and recurrence and metastasis rates were compared according to tumor location. Results The proportion of rectal cancer rose with invasion depth, from 16.2% (271/1673) in Tis to 18.5% (248/1337) in T1 and 26.4% (178/675) in T2 ( p < 0.01). Compared with T1 colon cancer, T1 rectal cancer showed higher rates of Ly1‐2 (35.1% vs. 27.4%), V1‐2 (37.9% vs. 24.6%), and recurrence (4.4% vs. 0.6%) (all p < 0.05). Similarly, T2 rectal cancer showed higher V1‐2 (68.5% vs. 54.1%) and recurrence rates (13.5% vs. 5.0%) compared with colon cancer (all p < 0.05). No significant differences were observed in lymph node or distant metastasis at either T1 or T2 stages. Conclusions Rectal cancers demonstrate more aggressive features and higher recurrence rates than colon cancers. Consequently, these patients require more stringent therapeutic approaches and rigorous postoperative surveillance, even in early stages. Trial Registration Umin Clinical Trials Registry, UMIN 000042622.