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Published on: February 12, 2022
Distal margin length after neoadjuvant chemoradiotherapy has no prognostic impact in low rectal cancer once the
Xiaojie Wang1, Weizhong Jiang1, Yanwu Sun1
1Department of Colorectal Surgery, Union Hospital, Fujian Medical University, People's Republic of China.
Background:
Although neoadjuvant Chemoradiotherapy (NCRT) has been used to shorten the distal resection margin (DRM) and enable sphincter preservation, the hypothesis that-once the margin is microscopically clear-DRM length itself no longer affects prognosis has never been tested in an equivalence trial. We examined whether any negative DRM length yields equivalent oncological outcomes.
Methods:
A total of 453 patients treated at 22 Chinese centres between 2013 and 2018 were included in this post-hoc study of the multicentre LASRE trial. All patients had clinical stage II-III low rectal adenocarcinoma (≤5 cm from dentate line), completed NCRT and underwent curative-intent sphincter-preserving resection. Fresh-specimen DRM was prospectively measured to the nearest millimetre.
Primary Endpoint:
3-year disease-free survival (DFS). Equivalence margins: HR 0.90-1.11. Two one-sided tests (TOST) used α = 0.05.
Results:
After exclusion of 5 patients with positive DRM, 73 (16.3 %) had DRM ≤1 cm, 160 (35.7 %) 1-2 cm and 215 (48.0 %) >2 cm. Three-year DFS (log-rank P = 0.155), locoregional recurrence (P = 0.386) and overall survival (P = 0.127) were comparable across groups. Adjusted HRs for DRM were 1.00 (95 % CI 0.98-1.01) for DFS, 0.98 (0.95-1.01) for OS and 1.00 (0.95 to 1.05) for local recurrence; all estimates lay within equivalence margins (TOST P < 0.05).
Conclusion:
Once the DRM is microscopically negative after NCRT, its length does not influence prognosis; sphincter-preserving surgery need not be deferred solely to obtain a longer margin.
Trial Registration:
Parent trial: ClinicalTrials.gov NCT01899547; distal margin length analysis protocol preregistered at Open Science Framework (Doi: osf.io/z8uab).
