Most anal lesions do not progress to cancer in MSM

Issue: May 10, 2012

Researchers in Australia have found that although men who have sex with men are at high risk for precancerous anal lesions, most of these lesions will not progress to cancer.

In HIV-positive men, the pooled prevalence of anal human papillomavirus type 16 was 35.4%. The incidence of anal HPV 16 was 13%, and clearance occurred in 14.6% of men per year.

“Although many studies have estimated the prevalence and incidence of anal HPV infection, anal cytological abnormalities and high-grade intraepithelial neoplasia in MSM, the natural history of progression of anal HPV infection to anal cancer in MSM is unclear,” the researchers wrote.

The meta-analysis included a search of PubMed, Ovid Medline and Embase for all studies published before November 2011 that reported prevalence and incidence of anal HPV detection, intraepithelial neoplasia and anal cancer in MSM. The search yielded 53 relevant studies, most of which were cross-sectional studies conducted in North America.

In 29 studies, HPV prevalence was described for HIV-positive MSM, and in 18 studies, HPV prevalence was described for HIV-negative men. The prevalence of anal HPV was higher in HIV-positive men compared with HIV-negative men (P=.005).

The pooled prevalence of high-grade intraepithelial neoplasia was 29.1%, with incidence of 8.5% and 15.4% per year in two of the studies. The pooled anal cancer incidence was 45.9 per 100,000 men per year.

In HIV-negative men, the pooled prevalence of anal HPV 16 was 12.5%. Incidence of HPV 16 was 11.8% and 5.8% of men per year in two of the studies. The pooled prevalence of high-grade intraepithelial neoplasia was 21.5%, with incidence of 3.3% and 6% in two of the studies. The incidence of anal cancer was 5.1 per 100,000 men.

“Large, good quality prospective natural history studies, coupled with randomized trials of treatment options, are needed to inform the development of anal cancer screening guidelines in MSM,” the researchers wrote. “Until evidence from these studies is available, screening for anal cancer and treatment of high-grade intraepithelial neoplasia should be done in only a research setting.”

In an accompanying editorial, Nicolas Wentzensen, MD, PhD, of the division of cancer epidemiology at the National Cancer Institute, compared the experience with HPV-related cervical cancer and HPV-related anal cancer, and he called for surrogate endpoints for anal cancer risk, similar to how cervical intraepithelial neoplasia grade 3 is a surrogate for cervical cancer risk.

“Molecular characterization of anal precancers identified at sites that do close surveillance of HIV-positive MSM populations and disease identified in natural history and biomarker studies will provide invaluable data to define anal precancers, before moving toward trials of screening and management modalities to screen for anal cancer,” Wentzensen wrote.”

References:

Machalek DA. Lancet Oncol. 2012;doi:10.1016/S1470-2045(12)70080-3.
Wentzensen N. Lancet Oncol. 2012;doi:10.1016/S1470-2045(12)70101-8.

Disclosures: Dr. Wentzensen reports no relevant financial disclosures. The researchers report the following disclosures: AEG has received honoraria and research funding from CSL Biotherapies, honoraria and travel funding from Merck, and sits on the Australian advisory board for the Gardasil. CKF has received honoraria, travel funding, and research funding from CSL Biotherapies and MSD, sits on the Australian advisory board for Gardasil HPV vaccine, and owns shares in CSL Biotherapies. SMG has received advisory board fees and grant support from CSL Biotherapies and GlaxoSmithKline, and lecture fees from Merck, GlaxoSmithKline, and Sanofi Pasteur; she has received funding through her institution to do HPV vaccine studies for MSD and GlaxoSmithKline and is a member of the Merck Global Advisory Board and the Merck Scientific Advisory Committee for HPV. RJH has received support from CSL Biotherapies and MSD. All other authors declare that they have no conflicts of interest.