How Does the Surgical Margin Status Affect the Association Between Mesorectal Excision Quality and Overall Survival in Patients With Locally Advanced Rectal Cancer? A Contemporary Analysis From the NCDB

Background The quality of mesorectal excision completeness is a key determinant of oncologic outcomes in rectal cancer; however, it is unclear how surgical margin status influences the survival impact of mesorectal excision quality. The present study aimed to assess the survival outcomes of incomplete total mesorectal excision (TME) in patients with locally advanced rectal cancer, according to surgical margin status. Methods Using a contemporary (2022–2023) cohort from the US National Cancer Database, adult patients with clinical stage II‐III rectal adenocarcinoma who underwent proctectomy were included. Complete and near‐complete TME were analyzed as a single group and compared with incomplete TME. Multivariable logistic regression was used to identify predictors of incomplete TME. Kaplan–Meier statistics and multivariable Cox proportional hazard analysis were used to assess 3‐year overall survival (OS), stratified by margin, stage, and neoadjuvant chemoradiation therapy (nCRT). Results Among 4889 patients (61.6% males), 12.6% had an incomplete TME. Incomplete TME was associated with higher rates of positive CRM (37.5% vs. 11.1%) and positive margins (39.7% vs. 12.5%). Incomplete TME was associated with reduced 3‐year OS (82.0% vs. 87.9%, p < 0.001). This survival decrement was more notable in patients with positive CRM (71.0% vs. 81.2%) than in patients with negative CRM (87.9% vs. 88.6%). The adverse survival effect of incomplete TME was strongest in patients who did not receive nCRT. Incomplete TME was not independently associated with reduced OS after adjustment for confounders (HR: 1.583, 95% CI: 0.892–2.807, p = 0.116). Conclusions Incomplete TME was not independently associated with significantly reduced OS. However, it may have an adverse survival effect in patients with positive CRM or who did not receive nCRT. Margin status was found to be a critical modifier of the TME‐survival relationship.