Rethinking surgical strategy for margin-positive only T1 colorectal cancer: a multicenter retrospective cohort study

Endoscopic resection is frequently performed for early T1 colorectal cancer (CRC), with additional surgery indicated when histopathological risk factors are present, such as a positive vertical margin, submucosal invasion depth greater than 1000 µm, lymphatic or vascular invasion, poorly differentiated adenocarcinoma, signet-ring cell carcinoma, mucinous carcinoma, or grade 2/3 tumor budding at the deepest invasive site. In patients undergoing radical resection for T1 CRC, the incidence of lymph node metastases(LNM) has been reported to be approximately 10%. The purpose of this study is to identify factors influencing the decision for radical resection in patients with pathologically confirmed T1 CRC following endoscopic resection and to evaluate lymph node metastasis rates according to each risk factor, with a focus on determining whether radical resection might be safely avoided in carefully selected low-risk cases.

The study was designed as a retrospective multicenter comparative cohort study conducted at three tertiary referral centers in Korea. The study population consisted of patients with pathological T1 colorectal cancer who underwent radical resection following endoscopic resection between April 2019 and December 2024. The main outcome measure was the incidence of lymph node metastasis according to pathological risk factors, with a particular focus on patients with margin-positive lesions without any other risk factors. Univariate analyses were performed, and exact binomial confidence intervals were calculated for the margin-positive subgroups.

Among 250 patients who underwent radical surgery after endoscopic resection, 25 (10.0%) had lymph node metastasis. Lymphovascular invasion and KRAS mutation were significantly associated with lymph node metastasis. Twenty-two patients with margin positivity without any other risk factors had no LNM (0/22; 95% exact binomial confidence interval, 0-15.4%). Half (11/22) of these patients had no residual tumors on surgical specimens, whereas the remainder showed only submucosal residual tumors without nodal involvement.

Among patients who underwent radical resection after endoscopic resection for T1 CRC, margin positivity without other recorded high-risk features was not associated with LNM in this cohort. However, given the small sample size and wide confidence interval, these findings should be considered hypothesis-generating and require further validation [1].