Intersphincteric resection versus transanal local excision after neoadjuvant therapy for ultra-low rectal cancer: a two-center retrospective propensity-score-adjusted cohort study

Objective To compare the long-term oncological outcomes and postoperative complications between local excision (LE) and intersphincteric resection (ISR) after neoadjuvant chemoradiotherapy (nCRT) in patients with ultra-low rectal cancer (ULRC). Methods Data were retrospectively collected from ULRC patients (tumor lower margin ≤5 cm from anal verge) who received nCRT followed by LE or ISR at two hospitals between 2016 and 2025. LE was selectively offered to patients achieving clinical complete response (cCR) or near-complete response (ncCR) after nCRT; ISR was the institutional default for incomplete responders. Propensity score matching (PSM) using 1:2 nearest-neighbor matching with a caliper of 0.2 on the standardized propensity score scale was performed. Results A total of 367 patients were enrolled (ISR, n=209; LE, n=158). After PSM, 91 and 56 patients remained, respectively. In the matched cohort, there were 20 deaths, 31 disease-free survival (DFS) events, 17 distant metastases (DM), and 12 local recurrences. No statistically significant differences were observed in overall survival (OS) (HR = 0.699, 95% CI: 0.247–1.977; P = 0.460), DFS (HR = 0.802, 95% CI: 0.369–1.745; P = 0.580), DM (HR = 0.260, 95% CI: 0.059–1.137; P = 0.054), or local recurrence (HR = 1.365, 95% CI: 0.432–4.310; P = 0.590). The LE group had higher rates of overall complications (55.4% vs. 29.7%; P = 0.002) and adapted wound dehiscence (32.1% vs. 13.2%; P = 0.006), predominantly driven by minor complications (Clavien-Dindo I–II: 44.6% vs. 17.6%); major complications were similarly infrequent (10.7% vs. 12.1%). Prophylactic stoma creation was performed in 90.1% of the ISR group versus 7.1% of the LE group (P<0.001). Among 24 LE patients with ypT2 or higher disease, 21 (87.5%) refused recommended salvage surgery. Conclusion No statistically significant differences in OS, DFS, DM, or local recurrence were detected between an initial LE and ISR after propensity-score adjustment. However, limited event numbers, residual confounding related to post-neoadjuvant response selection, and incomplete adherence to recommended completion surgery preclude conclusions of oncological equivalence or noninferiority. LE was associated with substantially less initial diversion but more local-excision-defect morbidity under the definitions used. The incidence of postoperative complications was higher after LE, but this was mainly driven by minor complications; surgeons should pay close attention to rectal wound dehiscence.