Anal cancer incidence rates among men and women with and without HIV in South Africa

Background About 7.5 million people in South Africa have HIV, but little is known about the association of HIV and anal cancer incidence. We examined anal cancer incidence in a large South African cohort of insured men and women. Methods We conducted a cohort study using reimbursement claims data from a South African medical insurance scheme (01/2011-07/2020) to assess anal cancer rates among people with and without HIV aged ≥18 years. We estimated adjusted hazard ratios (aHRs) for the association of HIV and incident anal cancer using flexible parametric survival models. Covariates included sex, age, calendar year, a history of genital warts and other sexually transmitted infections, and in women, cervical pre-cancer. Results We included 1,068,915 people of whom 69,985 (7%) were living with HIV. Over 3,933,145 person-years, 122 anal cancers were diagnosed (crude rate: 3.1/100,000 person-years; 95% confidence intervals [CI] 2.6-3.7). People with HIV had a four-fold higher anal cancer risk than people without HIV (aHR 4.43; 95% CI 2.44-8.04). While anal cancer rates were similar among men and women, older age (≥65 vs 45-54 years; aHR 5.01; 95% CI: 2.94-8.53), a history of genital warts (aHR 7.56; 95% CI: 2.28-25.07), and among women, a prior cervical pre-cancer diagnosis (aHR 5.70; 95% CI 1.75-18.58) were associated with a higher anal cancer risk. Conclusions In South Africa, men and women with HIV, older individuals, people with a history of genital warts, and women with a prior cervical pre-cancer diagnosis might benefit from prioritized access to anal cancer screening.