Background Anal cancer is an HPV-mediated neoplasia of the squamous epithelium of the anus. A hitherto unexplained feature of anal cancer epidemiology is its much higher frequency among women, who comprise nearly two thirds of cases.
Methods Cross-sectional study of women with a history of an HPV-mediated gynaecological neoplasia in Tasmania, Australia. Women presenting for follow-up gynaecological care had anal swab samples taken for anal cytology by Hologic Liquid ThinPrep and HR-HPV typing. Women with abnormal anal cytology were invited for high-resolution anoscopy (HRA). Covariates of anal outcomes evaluated by log-binomial and log-multinomial regression.
Results 163 women had anal swabs taken and comprised the study sample, of whom 40.0% had abnormal cytology (28.2% high-grade). Of the 50 women with abnormal anal cytology having an HRA, 64.0% had abnormal histology (26.0% high-grade). Of the 120 women having anal HPV typing done, 31.7% had HR-HPV carriage, the most common types being 51 (11.5%) and 16 (9.2%).
In addition to some known anal cancer risk factors, we found front-to-back (FTB) wiping was associated with significantly increased prevalence of cytological and histological abnormality and HR-HPV carriage, while dabbing post-toilet was significantly decreased prevalences of all anal outcomes, all robust to adjustment.
Conclusions We have shown here that post-toilet wiping behaviours, specifically FTB and dabbing, significantly modulated the prevalence of anal cytological, histological and HR-HPV carriage outcomes. While the cross-sectional design precludes ascription of causality, the biological plausibility of such an autoinoculation pathway might help explain the preponderance of anal cancer among women.
Conflicts of interest We have no conflicts to disclose.