27. Natural history of anal HPV in heterosexual women and risks associated with persistence

Abstract

Background: Anal cancer is more common in women than in men, yet little is known about the natural history of HPV in women. The objective was to examine the natural history of anal HPV in heterosexual women and to examine risk factors associated with persistence. Methods: Young women participating in a HPV cohort study were seen at 4-month intervals for cervical and anal testing for HPV DNA. The distribution of time to clearance was estimated using the Kaplan–Meier approach, and risks for persistence assessed using Cox regression models. Results: Seventy-five women (mean age 23.5 ± 4.1 years) who tested positive for anal HPV were followed for a mean of 84.5 ± 44.9 months. By 3 years, 82.5% of anal non-16 high risk (HR) HPV, 82.6% of low risk (LR) HPV and 76.2% of HPV16 infections had cleared. By 3 years, only 36.4% of women had become negative for all HPV types. In the multivariable model, concurrent cervical HPV 16 (P = 0.009) or any HR HPV (P = 0.046) detection, weekly alcohol use (P = 0.018), anal touching during sex (P = 0.034), and ever having anal sex (P = 0.06) were associated with HPV 16 persistence. Having a new sex partner (P < 0.001) and condom use during vaginal sex (P = 0.06) were associated with clearance. Similar associations were found for clearance all HR HPV infections. Only concomitant cervical HPV infection was associated with non-16 HR HPV persistence. Conclusions: The majority of anal HPV infections cleared within 3 years. HPV 16 infections were slower to clear than other HR HPV, consistent with its role in anal cancer. Sexual behaviour was associated with persistence, suggesting that education and behavioural interventions may decrease persistence and the risk of anal cancer.