According to a pair of recent studies, two of the most commonly used classes of medication —statins and nonsteroidal anti-inflammatory drugs (NSAIDs)—may compromise already controversial cancer screenings by lowering serum levels of prostate-specific antigen (PSA).

Researchers at Duke University, in Durham, N.C.,  conducted a longitudinal study of 1,214 men who filled statin prescriptions between 1990 and 2006. Most patients (95%) used simvastatin (Zocor); 20 mg was the most common initial dose (J Natl Cancer Inst. 2008;100:1511-1518).

Serum PSA levels declined by an average of 4.1% after statin therapy was started. The association appeared to be direct. Every 10% decrease in LDL was accompanied by a 1.64% decrease in PSA. In addition, men whose pre-statin PSA made them likely candidates for biopsy (>2.5 ng/mL) and who were in the top quartile for LDL reduction (>41%) experienced a 17.4% PSA decline.

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This effect “may complicate prostate cancer screenings because cancers may be missed due to the lower PSA levels,” the study authors observe.

Researchers at Vanderbilt University reached a similar conclusion about NSAIDs in the Nashville Men’s Health Study. The 1,277 participants were all older than age 40 years and scheduled for diagnostic prostate biopsy. About 46% of these men reported taking an NSAID, including 37% who specified they were taking aspirin.

After adjusting for other independent variables that affect PSA levels, prostate size, and cancer risk, PSA values were nearly 9% lower in men who took aspirin compared with those who did not (7.3 vs. 8.0 ng/mL).

“Many men take NSAIDs for their cardiovascular health, so we need to know whether these agents reduce prostate cancer risk or simply reduce PSA, which would then be even less reliable as a marker of prostate cancer risk,” notes lead investigator Jay H. Fowke, PhD, assistant professor of medicine at Vanderbilt University School of Medicine.