Nearly one-third of men with anal cancer have the human immunodeficiency virus (HIV), according to the results of a study published in the Journal of the National Cancer Institute.

Anal cancer is an uncommon type of cancer that occurs in the anal canal, the opening at the end of the rectum. The rate of anal cancer in the United States has been rising since 1940. Some groups are at a higher risk of developing anal cancer, including gay men, individuals with multiple sex partners over their lifetime, individuals with genital warts, and those who have had anal intercourse.

Infection with the human papillomavirus (HPV) is one of the major risk factors for anal cancer. (There are more than 100 different types of HPV and some strains of the virus have been linked with certain types of cancer.) HPV is estimated to cause about 85 percent of all anal cancer cases. Individuals with compromised immune systems—including those with HIV—are at a higher risk of developing HPV, and subsequently HPV-related cancers.

In order to determine the impact of HIV on anal cancer incidence in the U.S., researchers examined data from the HIV/AIDS Cancer Match Study—specifically the number of people with anal cancer with and without HIV between 1980 and 2005 in 17 U.S. states and metropolitan areas. They found that of 20,533 people with anal cancer, 8 percent were infected with HIV. Based on their estimations, the researchers found that from 2001 to 2005 1 percent of women and 28 percent of men with anal cancer were HIV-positive. To put that in perspective—less than 1 percent of people in the Unites States have the HIV infection, yet 28 percent of men with anal cancer have HIV.

The researchers concluded that HIV infection had a strong impact on the increasing anal cancer incidence rates among men, but not among women.

There may be a link between HPV and HIV infection. Because immunosuppressed individuals are at a higher risk of developing HPV—and subsequently, HPV-related cancers—prevention of HPV may be key among individuals with HIV. Currently, there is no standard approach for the prevention or early detection of HPV in this population; however, there are some new strategies being evaluated, including anal Pap tests and vaccination with the HPV vaccine. The vaccine is commonly used in young women in girls, but less often in young men and boys. Thus far, there have not been any definitive studies to evaluate the HPV vaccine among individuals with HIV to determine whether it could prevent anal cancer.

In light of the results of this study, it could make sense to screen all gay men—not just HIV-positive gay men—for anal cancer. Early detection of the cancer can reduce the risk of death.

Reference:

Shiels MS, Pfeiffer RM, Chaturvedi AK, et al. Impact of the HIV epidemic on the incidence rates of anal cancer in the United States. Journal of the National Cancer Institute. Published early online October 5, 2012. doi: 10.1093/jnci/djs371

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