Background: Incomplete mesorectal excision during rectal cancer surgery often leads to positive circumferential margins, with uncertain prognostic impacts. This study examines whether negative margins can mitigate the poorer prognosis typically associated with incomplete total mesorectal excision (TME) in rectal cancer surgery, thus potentially challenging the prevailing emphasis on complete mesorectal excision.

Patients and methods: A retrospective analysis was conducted on patients who underwent proctectomy for rectal adenocarcinoma with incomplete TME at a single center from 2010 to 2022. Patients were stratified by margin status as determined by pathologic analysis into three groups: involved, not involved with closest margin distance ≤ 2 mm, and not involved with closest margin distance > 2 mm. Outcomes included recurrence and survival. Effects of neoadjuvant therapy protocols on margin status were also assessed.

Results: From 2010 to 2022, 7941 patients underwent proctectomy for rectal cancer, with 236 (3%) having incomplete TME. The median age of these patients was 64 years, and 63% were male. Overall, margin involvement was observed in 54 (23%) patients. The median tumor size was 3.05 cm (interquartile range (IQR): 2-6) for the whole group. Involved margins (23.2%) had reduced overall survival (60.5 months versus 87.3 months, p < 0.001), increased local recurrence (20.4% versus 9.4%, p = 0.024), and lower disease-free survival (45.2 versus 58.9 months, p = 0.006) versus uninvolved margins. Margin involvement was prognostic for decreased survival even after adjusting for confounders (p < 0.05). Among uninvolved margins, distance (> 2 mm versus ≤ 2 mm) did not affect outcomes. Total neoadjuvant therapy (versus standard chemoradiation) was associated with lower involved margins (p = 0.007).

Conclusions: Positive margins retain negative prognostic impact with incomplete TME. Optimization of surgical resection remains vital. Total neoadjuvant therapy was associated with a lower rate of margin involvement.

Keywords: Incomplete TME; Margin status; Mesorectal excision; Neoadjuvant therapy; Rectal adenocarcinoma.

© 2025. The Author(s).