Roxanne Nelson

November 18, 2008

November 18, 2008 (Washington, DC) — The use of aspirin and other nonsteroidal anti-inflammatory drugs (NSAIDs) is significantly associated with lower levels of prostate-specific antigen (PSA). However, it is unclear whether the use of NSAIDs is actually decreasing the risk for prostate cancer, or whether it simply lowers PSA beyond the level of clinical suspicion, researchers reported here at the Seventh Annual American Association for Cancer Research International Conference on Frontiers in Cancer Prevention Research.

"This research tried to get a sense of the effect of NSAIDs on the incidence of prostate cancer, and results suggest there may be a benefit," explained Scott Lippman, MD, from University of Texas M.D. Anderson Cancer Center, in Houston. "But one of the issues here is whether drugs like aspirin are actually reducing the rate of prostate cancer or just changing detection bias," he said.

"While the data look good, we need to know if aspirin is really reducing the risk of prostate cancer," said Dr. Lippman, who moderated the press briefing in which the data were presented.

Previous research suggests that NSAIDs reduce prostate inflammation and prostate cancer risk. Low-dose aspirin is also commonly used to reduce the risk for cardiovascular disease. In this study, researchers evaluated the association between NSAID use, PSA levels, and prostate volume, and hypothesized that men using NSAIDs would have lower PSA levels and prostate volume.

"The have been a handful of studies that show an association between NSAID use and a reduced risk of prostate cancer," said lead author Jay H. Fowke, PhD, MPH, an assistant professor of medicine and cancer epidemiologist at Vanderbilt University Medical Center, in Nashville, Tennessee. "They've reported a 10% or 20% reduction in risk, and this runs across different NSAIDs, including aspirin and COX-2 inhibitors."

"We asked [whether] it's really affecting prostate cancer risk or just the detection of PSA levels," he told Medscape Oncology in an interview. "We conducted our study and found that men who were taking aspirin — which was the most commonly used NSAID — had lower PSA levels. This opened the window of discussion about whether NSAID use is really reducing cancer risk or whether we are just detecting it less efficiently. And that would show up as the protective effect seen in other studies."

The study cohort consisted of 1277 men who were participating in the Nashville Men's Health Study, a multicentered rapid-recruitment protocol that collected clinical, biological, behavioral, and body-measurement data from participants older than 40 years who were scheduled for diagnostic prostate biopsy. Information about NSAID use was obtained from surveys and interviews, and data concerning PSA levels, prostate volume, and clinical diagnoses after biopsy were obtained from medical charts.

The researchers found that about 46% of the men were using an NSAID, with the majority (37%) taking aspirin. After adjustment for confounders, such as age, race, family history of prostate cancer, obesity, and treatment for benign prostatic hypertrophy (BPH), cardiovascular disease, hyperlipidemia, or diabetes, aspirin use was significantly associated with lower PSA levels (7.3 vs. 8.0 ng/mL).

Aspirin use appeared to have the most effect on the PSA levels of men with a prostate volume of 60 mL or more, those who were diagnosed with prostate cancer (6.1 vs. 7.3 ng/mL), and those with both cancer and prostate enlargement. The use of NSAIDs was not significantly associated with prostate volume (47.6 vs. 46.0 mL).

"We did some subanalyses and found that aspirin use had no association with BPH. The association between aspirin and PSA was only really seen in men with prostate cancer," said Dr. Fowke. "We know that certain enzymes, like COX, are expressed in cancer cells,and that makes them a target for aspirin and other NSAIDs. So this fits with the idea that aspirin and other NSAIDs may be reducing prostate cancer risk."

Although this is consistent with the hypothesis that it is reducing cancer risk, it also opens the door for detection bias. "We really need to figure this out," said Dr. Fowke. "Are aspirin and other NSAIDs affecting the ability to detect cancer, are they reducing carcinogenesis, or it is occurring simultaneously? This will be the next obvious analysis."

Seventh Annual American Association for Cancer Research (AACR) International Conference on Frontiers in Cancer Prevention Research. Abstract A113. Presented November 16, 2008.

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