Long-term outcomes of pT1 rectal cancer after transanal endoscopic surgery: again, a word of caution on high local recurrence - a cohort study.

[PURPOSE] Recent evidence suggests that the local recurrence (LR) rate after local excision of pT1 rectal adenocarcinoma may be higher than previously estimated, particularly in large cohorts with extended follow-up. This study aimed to evaluate the LR rate and long-term oncological outcomes in patients with pT1 rectal adenocarcinoma treated with transanal endoscopic surgery (TES).

[METHOD] Observational cohort study including 824 consecutive patients who underwent TES at a single tertiary center between 2004 and 2021. Among them, 104 patients (12.6%) were diagnosed with pT1 rectal adenocarcinoma. Patients were excluded if they had received neoadjuvant or adjuvant chemoradiotherapy, had non-rectal tumors, a follow-up of less than 40 months, or were treated with surgical techniques other than TES.

[RESULTS] With a median follow-up of 91 months (IQR: 84), 17 patients (16.3%) developed LR and 14 (13.5%) developed distant recurrence. Five-year rectal cancer-specific and overall survival rates were 95% and 74%, respectively. Among the 88 patients without histopathological or surgical high-risk factors, 13 (14.8%) experienced LR and 9 (10.2%) distant recurrence. Their five-year disease-free and overall survival rates were 95% and 74%, Multivariate analysis identified flat-ulcerated morphology as the only independent predictor of LR (OR 6.8; 95% CI 1.5-30.4; p = 0.01).

[CONCLUSION] TES for pT1 rectal adenocarcinoma resulted in a 16.3% overall LR rate, and 14.8% among patients without known risk factors, emphasizing the need for improved patient selection and novel prognostic and therapeutic tools. These findings warrant confirmation in multicenter studies with standardized criteria and prolonged follow-up.