Human papillomavirus vaccines and anal carcinoma

Abstract

To explore the possible role of current prophylactic vaccines against human papillomavirus (HPV) in the prevention of anal intraepithelial neoplasia and squamous cell carcinoma of the anus (SCCA). SCCA incidence is increasing in several developed countries, particularly in HIV-positive men who have sex with men (MSM). Antiretroviral treatments against HIV do not seem to decrease SCCA risk. A meta-analysis of 955 SCCA showed that HPV prevalence was 85%, i.e., similar to that in cervical carcinoma, with an even stronger predominance of HPV16. In addition, more than 90% prevalence of HPV was found in anal intraepithelial neoplasia. Trials of the bivalent and quadrivalent vaccines against HPV16/18 have shown nearly 100% efficacy against high-grade lesions of the cervix, vulva and vagina in uninfected women under 26 years of age. The quadrivalent vaccine that includes HPV6/11/16/18 has also shown high efficacy against anogenital warts. Currently available HPV vaccines could potentially prevent the vast majority of SCCA, but only if administered before the onset of sexual activity. Answers to some still open questions, notably vaccine efficacy in men and HIV-infected individuals and willingness to expand vaccination programmes to both sexes, are essential to predict the ultimate impact of HPV vaccines on the prevention of cancerous and precancerous anal lesions.