BACKGROUND

Men who have sex with men (MSM) without HIV are known to be at elevated relative risk for Human papillomavirus (HPV)-associated anal cancer in comparison to men who have sex with women (MSW), but are poorly characterized in terms of anal cancer incidence due to absence of reporting of sexual behavior/identity at a population-level.

METHODS

By combining age-specific statistics from multiple data sources (anal cancer incidence among all males; anal cancer incidence among MSM and MSW with HIV; population size of men with HIV by sexual orientation), we developed a mathematical model to estimate anal cancer incidence, annual number of cases, and proportion by (a) sexual orientation (MSM versus MSW), (b) HIV status, and (c) age (<30, 30-44, 45-59, and ≥60 years).

RESULTS

Anal cancer incidence (per 100 000) among MSM without HIV was 1.4 (95% uncertainty interval [UI], 0.6 to 2.3), 17.6 (95% UI = 13.8-23.5), and 33.9 (95% UI = 28.3-42.3), at ages 30-44, 45-59 and ≥60 years, respectively. 19.1% of all male anal cancer occurred in MSM without HIV, increasing from 4% of anal cancer diagnosed at 30-44 years to 24% at ≥60 years; 54.3% occurred in MSW without HIV (increasing from 13% at age 30-44 to 67% at >60 years), and the remaining 26.6% in men (MSM and MSW combined) with HIV (decreasing from 83% at age 30-44 to 9% at >60 years).

CONCLUSIONS

These findings should inform anal cancer prevention recommendations in male risk groups, including, for the first time, for the important group of MSM without HIV.