FRIDAY, Oct. 5, 2012 (HealthDay News) -- New research on anal cancer, a rare disease that's often caused by a sexually transmitted virus, found that nearly one-third of men with this form of cancer were HIV-positive.
Men infected with HIV, the virus that causes AIDS, are more likely to also become infected with the human papillomavirus (HPV), which can cause both cervical and anal cancer.
The findings, published Oct. 5 in the Journal of the National Cancer Institute, point to the importance of screening HIV-positive men for anal cancer, said study co-author Dr. Eric Engels, a senior investigator with the U.S. National Cancer Institute. "In the United States, fewer than 1 percent of people have HIV infection. Yet when you look at anal cancer, 28 percent of all cases in men are in those who have HIV."
According to background information in the study, anal cancer is diagnosed in about 6,000 people a year in the United States, mostly women, and kills around 700. Early detection, however, can lower the risk of death.
The anal cancer rate has been rising in the United States since 1940, the study authors pointed out, and several groups -- gay men, those with multiple sexual partners over their lifetime, those who've had genital warts, and those who have anal intercourse -- are at highest risk.
In the new study, researchers examined medical records from several states from 1980 to 2005 and found, over the entire period, that an estimated 8 percent of 20,533 anal cancer patients were infected with HIV. From 2001 to 2005, they estimated that 1 percent of women and 28 percent of men with anal cancer were HIV-positive.
The study suggests that there's a link between HPV and HIV infection. HPV is estimated to cause about 85 percent of anal cancer cases, Engels said. The virus can cause cells to make genetic changes and become cancerous.
HPV is transmitted through skin-to-skin contact, such as sexual activity. But people don't need to be on the receiving end of anal sex to develop an infection in the anal area. A person could transmit the virus from another part of the body, such as the genitals, to the anus, Engels explained.
What to do? There is no treatment or cure for HPV, according to the U.S. Centers for Disease Control and Prevention. However, "if one could prevent anal cancer in men with HPV, it would have a noticeable impact on the overall national burden of anal cancer," Engels said.
One way to do that is to use Pap tests -- which detect cervical cancer in women -- to screen HIV-infected people for anal cancer. "There is debate about whether that will be an effective approach," he said. "It's something that's being looked at."
Another strategy is to give people the vaccine series that prevents HPV infection. Young women and girls are frequently vaccinated because HPV can lead to genital warts and cervical cancer, but the vaccination is not as common among young men and boys.
However, Engels said, "there haven't been definitive studies in people with HIV to know whether the HPV vaccine will prevent anal cancer."
Commenting on the study, Dr. Joel Palefsky, a professor of medicine at the University of California, San Francisco, said the findings make sense. He recommends anal cancer screening not only for HIV-positive gay men but for all gay men.
Anal Pap tests are appropriate for HIV-positive men and older gay men, although there aren't federal guidelines for gay men, and doctors may not get reimbursed for the procedures, Palefsky said. He also recommends that physicians perform so-called digital exams in the rectum to look for signs of anal cancer in gay men.
These examinations are commonly performed to look for signs of prostate cancer, but physicians may not focus on also detecting anal cancer, Palefsky added.
For more about anal cancer, visit the U.S. National Library of Medicine.