NSAID Prostate Cancer Benefits Greatest In Older Men – Mayo Clinic Study

Daily nonsteroidal anti-inflammatory drug (NSAID) use resulted in an 83% reduced risk of prostate cancer in white men ages 70 to 79, a study in the March Mayo Clinic Proceedings found.

While the protective effect of NSAIDs was statistically significant in men over 50, "when stratified by age group, the association between daily NSAID use and prostate cancer was greatest in men who were 70 to 79 years old at the onset of the study," Mayo Clinic researchers Rosebud Roberts, et al., report.

Men in their sixties who took NSAIDs daily were 60% less likely to develop prostate cancer than those who did not take NSAIDs, while men in their fifties taking NSAIDs only experienced a 12% reduced risk for the disease, the researchers found.

To explain the differences in the age groups, Roberts et al. point out men over 70 "are more likely to have chronic...conditions such as osteoarthritis or heart disease that require treatment with NSAIDs. Therefore, they may have had a longer duration of NSAID use or a higher cumulative dose...than younger men."

Another reason may be that "the overall effects of NSAIDs...[are] to prevent the progression of latent prostate cancer," they suggest.

"Preclinical prostate cancer may be present even before men begin using NSAIDs on a daily basis," Roberts et al. explain, because the prevalence of latent prostate cancer "increases from 8% in men in their third decade to about 40% in the fifth decade."

As a result, "because the protective effects in our study were observed to be greater in older than in younger men, NSAIDs may prevent the progression of preclinical disease to clinically detectable disease but may not influence initiation," the researchers state.

However, Roberts et al. note "the biological mechanisms underlying the potential effects of NSAIDs on prostate cancer risk need to be investigated further."

The study involved 1,362 men over 50 from the Olmsted (Minn.) County Study of Urinary Symptoms & Health Status, a prospective cohort study to evaluate long-term outcomes of lower urinary tract symptoms.

Investigators reviewed the men's medical records for exclusion criteria, which included "a history of prostate cancer, prostate surgery, urethral stricture or surgery, bladder cancer or surgery, or other medical conditions known to affect normal urinary tract function except benign prostatic hyperplasia."

Roberts et al. note the study was limited to white men "because the Olmsted County minority population was too small at the onset of the study to allow the estimation of race-specific risk estimates."

Structured interviews given at baseline and at two-year intervals elicited information on current daily medication intake and family history of prostate cancer. Each patient was asked to report use of all Rx and OTC medications taken on a daily basis, as well as any new diagnosis of prostate cancer.

The researchers also conducted a retrospective review of study participants' medical records to confirm self-reported prostate cancer. Only men with a "histologically proved diagnosis" of the disease after five-and-a-half years of study were considered to have prostate cancer in the analyses.

The research was supported by grants from the National Institutes of Health and Merck Research Labs.

Roberts et al. found 4% of NSAID users and 8.6% of non-users developed prostate cancer during follow-up. "In person-year analyses, the incidence of prostate cancer was 8.4 per 1,000 person-years and 18.5 per 1,000 person-years in NSAID users and non-users, respectively," they report. The majority of men taking NSAIDs on a daily basis were aspirin users (87.5%).

Despite the positive findings, Massachusetts General Hospital physician Michael Barry cautions in an editorial that "the type of men who take low-dose prophylactic aspirin [may] have other health behaviors that reduce their risk for prostate cancer."

He notes that use of selenium and vitamin E, which also have been shown to reduce the incidence of prostate cancer, were not tracked and "may confound the relationship between aspirin intake and a subsequent prostate cancer diagnosis."

Roberts et al. agree further research is needed to "determine the effects of duration of use and cumulative dose, and provide insights into the mechanisms by which NSAIDs may influence the risk of prostate cancer." Research in men at high risk for the disease, such as African-Americans, is needed as well "to determine if similar biological mechanisms for prostate cancer exist in these men," they write.