July 22, 2009
ARV Therapy of Little Benefit in Preventing Anal Cancer
by Tim Horn
ARV therapy may not afford much protection against anal cancer among HIV-positive people, according to sobering study results reported Wednesday, July 22, at the Fifth International AIDS Society (IAS) Conference on HIV Pathogenesis, Treatment and Prevention in Cape Town. In fact, according to the Veterans Administration analysis reported by Nancy Crum-Cianflone, MD, of the Naval Medical Center in San Diego, rates of anal cancer are progressively increasing.
Since potent antiretroviral (ARV) drug combinations began prolonging lives of HIV-positive people in the late 1990s, cancers originally not linked to HIV have become more prevalent in patients otherwise responding well to HIV treatment. Researchers have long suspected that anal cancer appears to occur at higher rates among HIV-infected people. What hasn’t been clear, however, is whether ARV therapy potentially reduces the risk of anal cancer—perhaps by boosting the immune response to better control human papillomavirus infection, a leading cause of anal cancer—or whether ARV therapy has little effect on its incidence.
The study reported by Crum-Cianflone evaluated rates of, and risk factors for, anal cancer—squamous cell carcinomas—using data from a VA cohort study started in 1985. A total of 5,029 HIV-positive individuals were included in the analysis.
According to Crum-Cianflone, anal cancer rates increased fivefold from the early years of the epidemic from 17 per 100,000 patient years (PYs) to 91 per 100,000 PYs with the advent of combination ARV therapy in the late 1990s. Rates of new anal cancer diagnosis in the cohort continued to increase at an astonishing rate, reaching 244 per 100,000 PYs in 2006 to 2008.
Twenty HIV-positive individuals were included in the analysis looking at anal cancer risk factors. The average age at the time of diagnosed was 41. About 95 percent were male; 55 percent were white; 50 percent had a history of hepatitis B infection; 41 percent had a history of gonorrhea; and 10 percent had a history of syphilis.
The average CD4 count at the time of diagnosis was 375 cells. Forty-one percent had viral loads below 400 copies; 40 percent had an earlier AIDS-related complication; and 75 percent were receiving ARV therapy.
After completing the statistical analysis, Crum-Cianflone’s team found those with anal cancer were more likely to have an earlier AIDS-related complication, a lower CD4 count and a history of more sexually transmitted infections.
ARV therapy, Crum-Cianflone said, was not shown to effectively reduce the risk of anal cancer in this study.
As HIV patients are living longer, Crum-Cianflone warned, it may allow for sufficient time for anal cancer development, hence rates may continue to increase. She stressed the need for preventive strategies, such as more aggressive screening for precancerous lesions and for anal carcinoma among HIV-infected people.
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