June 3, 2014
The risk of prostate cancer was found to be 27% lower in HIV-positive men when compared to their HIV-negative counterparts, according to a study published in the Journal of Acquired Immune Deficiency Syndromes.
The study, which followed 17,424 HIV-positive men and 182,799 HIV-negative men enrolled in Kaiser Permanente, compared the incidence of prostate cancer while adjusting for confounding factors, including age, race, smoking, alcohol/drug abuse, being overweight/obese and having diabetes.
Prostate cancer was diagnosed in 74 HIV-positive and 1195 HIV-negative men. Differences according to HIV status were observed. Men living with HIV were more likely to be diagnosed with less advanced cancers (state II, 95 vs 89%; stage III-IV, 5 vs 11%) and to have localised (93 vs 83%) rather than regional/distal (3 vs 14%) cancers. Recent PSA [prostate-specific antigen] levels were lower among men living with HIV (10 vs 17).
Overall incidence of prostate cancer was 102/100,000 person-years for men living with HIV compared to 131 per 100,000 person-years for HIV-negative men. After controlling for potential confounders, men living with HIV had a 27% reduction in the risk of prostate cancer (RR = 0.73; 95% CI, 0.57-0.92). The association between HIV infection and a reduced risk of prostate cancer was strongest for more advanced cancers (stage III/IV, RR = 0.28; 95% CI, 0.009-0.90; regional/distal cancers, RR = 0.28; 95% CI, 0.11-0.68). However, men living with HIV also had a reduced risk of less severe forms of cancer (stage II, RR = 0.77; 95% CI, 0.60-1.01; localised cancers, RR = 0.81; 95% CI, 0.63-1.05).
"Our results suggest that the observed lower incidence of prostate cancer among HIV-positive men in this setting is attributable to factors other than differences in PSA screening or the risk factors evaluated," the researchers wrote.
"One viable explanation may be that ART [antiretroviral] use, specifically Pis [protease inhibitors], protects against the development of prostate cancer," the authors hypothesized. "It may also be that MSM [men who have sex with men], who comprise a substantial proportion of the HIV-positive men in industrialized countries, have more favorable nutrition, weight, or exercise patterns, which can reduce the risk of cancer. Although we did not see a difference in incidence by sexual orientation, the prevalence of heterosexual men was low and we did not have data to identify contributing factors among MSM."
Although effective HIV treatment has led to people with HIV living longer and healthier lives, diseases associated with aging are a mounting concern. Therefore, this finding is welcome news for men living with HIV. However, the authors noted that the reason for this reduced risk remains unclear, and suggested further research to explore the underlying mechanisms, as well as comparison of prostate cancer risk among HIV-positive and HIV-negative MSM in environments where there is detailed collection of behavioral data.
Warren Tong is the research editor for TheBody.com and TheBodyPRO.com.
Follow Warren on Twitter: @WarrenAtTheBody.
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