Stage-dependent differences of long-term outcomes between chemoradiotherapy and surgery for squamous cell carcinoma of the anal canal: a multicenter retrospective cohort study.

OBJECTIVES: Efficacy comparisons between surgery and chemoradiotherapy (CRT) in the treatment of squamous cell carcinoma (SCC) of the anal canal have not been performed enough. Herein, we aim to reveal the long-term outcomes of CRT and surgery for SCC of the anal canal and to assess the optimal clinical stage-dependent treatment strategy. METHODS: We retrospectively assessed patients with SCC who were treated via CRT or surgery between 1991 and 2015 at 47 medical institutions in Japan. The associations of the treatment strategy with the overall survival (OS) and the cumulative incidence of the first recurrence categorized as local failure, inguinal lymph node metastasis, or distant recurrence were examined. RESULTS: The OS following CRT and surgery for clinical stages ≤ II were similar (adjusted hazard ratio [aHR] 0.89, 95% confidence intervals [CI] 0.48-1.63); however, surgery was associated with lower OS for clinical stage III (aHR 1.82, 95% CI 1.06-3.11). Local failure was more likely to occur after CRT, and inguinal node metastasis occurred more frequently after surgery. CONCLUSIONS: Optimal treatments for anal canal SCC differ by clinical stage. Despite lacking QOL and organ preservation data, surgery might be an alternative option for stage I-II disease regarding long-term survival. More rigorous comparative studies are warranted.