Salvage abdominoperineal resection for anal squamous cell carcinoma after radiotherapy or chemoradiotherapy: analysis of the French prospective cohort FFCD-ANABASE.

Introduction: Salvage abdominoperineal resection (APR) is indicated for local failure following definitive chemoradiotherapy or radiotherapy for squamous cell carcinoma (SCCA), at the cost of morbidity and reduced quality of life. This study evaluated outcomes after salvage APR.

Materials and methods: The FFCD-ANABASE cohort is a prospective multicenter cohort including patients treated for non-metastatic SCCA in France between 2015 and 2020. Among the 1015 patients included in FFCD-ANABASE, 78 underwent salvage APR. After excluding patients with a pathological complete response (pT0N0), the final efficacy analysis cohort comprised 66 patients. We analyzed disease-free survival (DFS), overall survival (OS), locoregional and metastatic relapse rates, post-operative morbidity and prognostic factors in patients who underwent salvage APR for local failure.

Results: With a median follow-up of 58.6 months after APR, the locoregional relapse rate was 21.2 % and the metastatic relapse rate was 9.1 %. An R0 resection was achieved in 80.8 % of cases. Five-year DFS and OS rates were 45.8 % [95 %CI: 33.3-57.4], and 50.2 % [95 %CI: 37.1-62.0]. In multivariate analysis, R0 margins (HR: 0.24 [95 %CI: 0.10-0.61]), and tumor size before chemoradiotherapy <4 cm (HR: 0.33 [95 %CI: 0.12-0.91]) were associated with better DFS; whereas no factor was significantly associated with OS. Post-operative morbidity was reported in 65 patients (83.3 %), with 34 of them (52.3 %) experiencing major complications, classified as Clavien-Dindo III-V.

Conclusions: Salvage APR results in high post-operative morbidity and poor oncological outcomes. Our study found that complete resection margins was favorable prognostic factor, suggesting the need for additional perioperative treatment.