AIDS linked with reduced prostate cancer risk
MedWire News: US study findings show that men with AIDS have a reduced risk for prostate cancer compared with men in the general population, which the researchers suggest could be a result of reduced prostate-specific antigen (PSA) screening among HIV-infected men.
Meredith Shiels (National Cancer Institute, Rockville, Maryland) and colleagues found that rates of prostate cancer were decreased in men with AIDS attending their center during the era after PSA testing became commonplace.
"A sharp increase in prostate cancer incidence in the general population has largely been driven by widespread PSA screening, a practice that seems to be less frequently utilized for HIV-infected men," write Shiels et al in the journal Cancer Epidemiology Biomarkers and Prevention.
Past studies have suggested that HIV infection may prevent the development of prostate cancer through reductions in androgen levels.
Shiels and team compared prostate cancer incidence among a cohort of 287,247 US men with AIDS with that for the general population. Cancer risk was determined in the era prior to the introduction of PSA screening (1980-1991) and in the PSA era (1991-2007).
While prostate cancer rates increased over time in the general population after 1990, standardized incidence ratios (SIRs) confirmed that men with AIDS had the same prostate cancer rates as those for the general population in the pre-PSA era, but a significantly reduced rate in the PSA era, with SIRs of 1.00 versus 0.50.
Specifically, the reduction in prostate cancer incidence among men with AIDS was limited to local- and regional-stage cancers, at SIRs of 0.49 and 0.14, respectively, which the researchers note are those "most likely to be detected by PSA screening."
In addition, among men with AIDS followed-up during the PSA era, local and regional prostate cancer was not associated with an increased risk for death (hazard ratio=0.93), whereas distant stage increased men's risk for death 4.73-fold.
The researchers note that PSA testing among a cohort of HIV-infected men aged 40 years and above was uncommon, at 18.7% per year, although this increased 2.4-fold after age adjustment between 2000 and 2008.
Shiels and team believe their findings make it unlikely that HIV exhibits "a protective effect" against the development of prostate cancer.
They conclude: "We speculate that the low rates of screening reflect the clinicians' perception that the historically poor prognosis of HIV-infected men would limit the utility of the test, coupled with challenges in addressing other medical and social issues in this population."
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By Sarah Guy