Salvage APR for anal squamous cell carcinoma: Utilization, risk factors and outcomes in a Canadian Population.

BACKGROUND: Previous studies have reported that 30-40% of patients with squamous cell carcinoma of the anus will require salvage abdominoperineal resection following chemoradiotherapy. OBJECTIVE: To identify the utilization, risk factors and impact on survival of salvage abdominal perineal resection for squamous cell carcinoma of the anus. DESIGN: Retrospective, population-based cohort study. PATIENTS: All incident cases of squamous cell anal cancer who underwent curative intent radiotherapy from 2007-2015. SETTING: Patients treated in Ontario, Canada, a single payer universal health care system. MAIN OUTCOME MEASURES: Risk of salvage abdominoperineal resection, factors associated with salvage abdominoperineal resection and survival. RESULTS: A total of 1125 patients were treated with curative intent radiotherapy for squamous cell cancer of the anus. Within this cohort, salvage surgery was performed in 8% (93/1125), while 14% (156/1125) required a permanent colostomy. In log-binomial regression, younger age was associated with salvage surgery, while sex, cancer stage, socioeconomic status and HIV were not. There was a suggested lower risk of salvage surgery in those who completed chemoradiation (RR 0.67, 95%CI 0.43 - 1.03). Crude 5-year overall survival rate was 73% (95% CI: 70 - 76%) in those not requiring salvage surgery and 48% (95% CI: 37 - 58%) in those that did. In Cox models mortality was higher in patients requiring salvage surgery compared to those who did not (adjusted HR 2.20, 95%CI: 1.65 - 2.94), while improved survival was seen in those who completed chemoradiation (HR 0.65, 95%CI 0.42 - 0.82) LIMITATIONS:: Potential residual confounding by indication for salvage surgery. CONCLUSIONS: In this large, contemporary cohort of patients with squamous cell carcinoma of the anus, the proportion of patients undergoing salvage surgery was considerably lower than previous reports. Younger age was associated with salvage surgery, and there was a suggestion of lower risk of salvage surgery with completion of chemoradiation. Patients requiring salvage surgery had poor 5-year overall survival. See Video Abstract at http://links.lww.com/DCR/B205.