Sept. 30 (HealthDay News) -- Non-AIDS-related cancers such as anal and lung cancer have become more common among HIV patients than among people without HIV since antiretroviral therapies were introduced in the mid-1990s to treat people with the virus, U.S. researchers say.

Because of their weakened immune system, AIDS patients are at increased risk for so-called AIDS-defining malignancies, which include cancers such as cervical carcinoma, non-Hodgkin's lymphoma and Kaposi's sarcoma.

There has been speculation that non-AIDS-defining malignancies are becoming more common among HIV patients because antiretroviral drugs help them live longer. But this new study by researchers at University of Texas Southwestern Medical Center in Dallas suggests other factors may exist.

The researchers analyzed 1997 to 2004 data from more than 100,000 patients in the U.S. Veterans Affairs Healthcare System and found that HIV-infected patients were 60 percent more likely to have anal, lung, Hodgkin's, melanoma or liver cancer than patients without HIV.

"It's a genuine increase in the incidence of these cancers," lead author Dr. Roger Bedimo, an assistant professor of internal medicine, said in a university news release. "The increase is more visible because these patients are living longer, but our findings suggest that the increased number of non-AIDS-defining malignancies is not simply the result of their longer lives."

The study appears online and in the October print issue of the Journal of Acquired Immune Deficiency Syndromes.

One controversial theory is that antiretroviral therapy itself may increase the risk of non-AIDS-defining malignancies, the study authors noted.

"The second hypothesis is that HIV-infected patients somehow, either by their lifestyle or other circumstances, are more subject to the traditional risk factors than non-HIV patients," Bedimo said. "The third hypothesis is that HIV or another undetected virus increases a patient's risk for developing cancer intrinsically."

SOURCE: University of Texas Southwestern Medical Center, news release, Sept. 25, 2009