Although anal cancer is rare in the general population, its incidence is unacceptably high in people living with HIV. Among people over 45 years of age living with HIV, incidence rates are 100 per 100,000 person-years in men who have sex with men (MSM), 37 per 100,000 person-years in men who have sex with women (MSW), and 30 per 100,000 person-years in women.
Several international health organizations have recommended early detection of anal cancer to reduce morbidity and mortality from this type of cancer.
Screening includes a digital rectal exam to detect masses and collection of anal swabs for cytology and human papillomavirus (HPV) testing. If any abnormalities are detected, patients are referred for high-resolution anoscopy (HRA), a procedure similar to colposcopy, where the anus is examined under magnification to detect precursors to anal cancer (high-grade squamous intraepithelial lesions) and biopsies are taken using HRA-guided techniques.
Joel Palefsky, MD, of the University of California, San Francisco, in a special session at the Virtual Conference on Retroviruses and Opportunistic Infections, reported that histologically confirmed high-grade squamous intraepithelial lesions can be treated to decrease the risk of progression to anal cancer. The incidence of anal cancer was 173 versus 402 per 100,000 patient-years in the two respective arms.
"Treating anal HSIL is effective in reducing the incidence of anal cancer," he said, adding that the findings support screening for and treating anal HSIL as a standard of care for people living with HIV.
Palefsky and his colleagues commented that they “weren’t entirely happy with the high cancer rate in the treatment arm. There were some treatment failures, as also happens when treating HSIL in cervical cancer.” None of the patients in the study died from anal cancer. “About a third of the patients in each group had advanced cancer when they were diagnosed, so it was disappointing that it occurred within the treatment group.”
Study details
From September 2014 to August 2021, researchers evaluated 10,723 people living with HIV at 15 sites in the U.S. If a biopsy was positive for HSIL, patients were randomized by study site, CD4 cell count, and lesion size.
During the selection process, 17 people were found to have anal cancer.
Overall, the participants had an average age of 51 years and had been living with HIV for an average of 17 years. Approximately 80% of the participants were men, 16% were women, and 3.8% identified as transgender.
Immediate treatment (n = 2237) most frequently consisted of office electrocautery ablation of the HSIL (93% of cases). These patients were then biopsied if there was suspicion that the HSIL was still present. Anal cytology was performed every 6 months after resolution of the HSIL. The interval was shortened if cancer was suspected, and biopsies could be performed at any visit if cancer was suspected.
In the active monitoring group (n=2222), patients underwent anal cytology every 6 months and annual biopsies to confirm persistent HSIL, but returned every 3 months if the doctor was concerned about the development of cancer.
Once again, biopsies were performed on any visit where there was a concern about cancer.
Men diagnosed with anal cancer during screening tests had better survival rates, likely because they were diagnosed at an earlier stage of the disease. In addition to preventing anal cancer, this data provides strong justification for screening individuals at higher risk for the disease.