Regular use of aspirin, ibuprofen, and other non-steroidal anti-inflammatory drugs may protect against the development of prostate cancer in older men, says a study in the United States.
Men aged over 60 who took a daily dose of one of the drugs known collectively as non-steroidal anti-inflammatory drugs (NSAIDs) were half as likely to develop the disease.
The six year study of 1362 white men in Minnesota aged 50 to 79 found that 4% of men who took the drugs developed prostate cancer, compared with 9% of the control group (Mayo Clinic Proceedings 2002;77:219-25). The older the patient, the more pronounced the protective effect of the drugs. Patients were not, however, randomised to treatment, leaving open the possibility that something other than the drugs explains the difference between the two groups.
As part of the study, an interviewer ascertained each participant's daily medication regime. Armed with that information, Dr Rosebud Roberts, an epidemiologist and assistant professor at the Mayo Clinic, in Rochester, Minnesota, and her colleagues then followed their participants for up to six years. At the end of the study the researchers found that 23 (4%) of the 569 participants who regularly used NSAIDs developed prostate cancer, compared with 68 (9%) of the 793 participants who did not use the drugs on a daily basis.
The relative odds of prostate cancer in users of NSAIDs, compared with non-users, were 0.45 (95% confidence interval 0.28 to 0.73). This inverse association with use of NSAIDs increased with increasing age at the outset of the study. Although it is not clear how the drugs contributed to the lower cancer rates, previous laboratory experiments have shown that non-steroidal anti-inflammatory drugs block the action of an enzyme that triggers the production of prostaglandins, which are thought to be associated with prostate cancer.
Prostaglandins are believed to increase the carcinogenic potential of cells through the oxidation of pre-carcinogens to carcinogens, increased cell growth, decreased apoptosis or cell death, and a decreased immune response to abnormal cancer cells. The antineoplastic effects of NSAIDs may also occur through increased production of ceramide, a potent stimulator of apoptosis.
Several studies have already reported a decreased risk of colon cancer in patients who use NSAIDS. Other cancers for which similar associations have been reported include tumours of the rectum, oesophagus, breast, and ovary.
While the current findings are promising, it's too soon to recommend that older men begin taking aspirin, ibuprofen, or similar drugs, said Dr Roberts. In particular, the study's results cannot be reliably extended to black patients, the group with the highest risk of prostate cancer. Because the target population included only a small number of people from ethnic minorities, and therefore meaningful comparisons across race would have been difficult to achieve, the researchers decided to exclude non-white patients from the study.
"We also need to determine the duration and dosage that provide protection against prostate cancer, and to better understand the biological mechanisms underlying the association between NSAIDs and prostate cancer," she said.