The Association Between Sex and Survival for Anal Squamous Cell Carcinoma

Background: The incidence of anal squamous cell carcinoma (SCC) is rising, despite the introduction of a vaccine against human papillomavirus (HPV), the most common etiology of anal SCC. The rate of anal SCC is higher among women and sex-based survival differences may exist. We aimed to examine the association between sex and survival for stage I-IV anal SCC.

Materials and methods: The National Cancer Database was used to identify patients with stage I-IV anal SCC from 2004-2016. Outcomes were assessed utilizing log rank tests, Kaplan-Meier statistics, and Cox proportional-hazard modeling. Subgroup analyses by disease stage and by HPV status were performed. Outcomes of interest were median, 1-, and 5-year survival by sex.

Results: There were 31,185 patients with stage I-IV anal SCC. 10,714 (34.3%) were male and 20,471 (65.6%) were female. 1- and 5- year survival was 90.2% (95% CI 89.8 - 90.7) and 67.7% (95% CI 66.9 - 68.5) for females compared to 85.8% (95% CI 85.1 - 86.5) and 55.9% (95% CI 54.7 - 57.0) for males. In subgroup analysis, females demonstrated improved unadjusted and adjusted survival for all stages of disease. Female sex was an independent predictor of improved survival (HR 0.68, 95% CI 0.65 - 0.71, P < 0.001).

Conclusions: We demonstrate better overall survival for females compared to males for stage I-IV anal SCC. It is not clear why women have a survival advantage over men, though exposure to prominent risk factors may play a role. High-risk men may warrant routine screening for anal cancer.