Taking selenium supplements, aspirin, or ibuprofen, and eating plenty of vegetables may ameliorate a genetic predisposition to developing prostate cancer, according to a recent study, but it’s too soon to recommend changes to clinical practice.1
A research team led by Stacy Loeb, MD, of the Department of Urology at New York University, in New York, NY, conducted a case-control study using data from the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial.
The team analyzed data from 1,230 men with prostate cancer and 1,361 age-matched controls, all non-Hispanic whites age 55 to 74. Participants completed a questionnaire detailing their diet, supplement use, and other lifestyle factors and underwent annual PSA testing and digital rectal examination.
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From the subjects’ blood samples the researchers analyzed the presence of 20 single nucleotide polymorphisms (SNPs) known to increase prostate cancer risk and determined that men with 12 or more of the identified alleles had a greater risk of advanced or non-advanced prostate cancer.
But genetics isn’t fate: the researchers found that certain lifestyle factors reduced the incidence of prostate cancer in men at high genetic risk.
The effect was most striking for selenium. Men with 12 or more risk alleles who took selenium supplements had the same risk of developing advanced prostate cancer as men with less than 12 risk alleles.
High-risk men who took aspirin or ibuprofen or had a high vegetable intake were able to attenuate the risk of non-advanced disease, but not of advanced disease. Nevertheless, their risk of non-advanced disease was still 70% higher than that of men with less than 12 risk alleles.
As the researchers acknowledge, these results are intriguing but not definitive. The news about selenium is surprising, given the results of the SELECT trial, which found no benefit, and possible harm, from high-dose selenium for prevention of prostate cancer.2
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Moreover, it’s unclear from these results whether selenium, aspirin, ibuprofen, and vegetables actually reduce the incidence of prostate cancer or only reduces its detection by, for example, lowering serum PSA levels.
Finally, since this study included only non-Hispanic whites, its findings may not be generalizable to other populations.
Aspirin May Reduce Mortality in High-Risk Prostate Cancer
More positive, but inconclusive, evidence for the benefit of aspirin comes from a prospective study of more than 8,000 men who developed non-metastatic prostate cancer while enrolled in the Cancer Prevention Study-II Nutrition Cohort.3 The men were surveyed on aspirin use at enrollment in 1992 or 1993 and every 2 years thereafter and followed until 2010.
During follow-up of approximately 6 to 9 years, the researchers found no association between use of aspirin and mortality from prostate cancer. Subset analysis, however, demonstrated that among men diagnosed with high-risk cancers (stage T3 or higher and Gleason score ≥8), aspirin use following diagnosis was associated with lower prostate cancer-specific mortality (hazard ratio [HR], 0.60; 95% CI: 0.37,0.97).
This study should not prompt men with high-risk prostate cancer to start an aspirin regimen, however. “At best,” said Marc Garnick, MD, a professor of medicine at Harvard Medical School in Boston, MA, who was not involved in the study, “this is hypothesis-generating and is in no way practice-changing.” Dr. Garnick pointed out that there was no hypothesis as to why aspirin would affect prostate cancer mortality and the results could be due to chance alone.
Prostate cancer patients “should not take aspirin with the expectation that it will decrease mortality,” Dr. Garnick said.
References
- Loeb S, Peskoe SB, Joshu CE, et al. Do environmental factors modify the genetic risk of prostate cancer? Cancer Epidemiol Biomarkers Prev. 2014 Oct 23. [Epub ahead of print]. doi: 10.1158/1055-9965.EPI-14-0786-T.
- Lippman SM, Klein EA, Goodman PJ, et al. Effect of selenium and vitamin E on risk of prostate cancer and other cancers: the SSelenium and Vitamin E Cancer Prevention Trial (SELECT). JAMA. 2009;301(1):39-51.
- Jacobs EJ, Newton CC, Stevens VL, et al. Daily aspirin use and prostate cancer–specific mortality in a large cohort of men with nonmetastatic prostate cancer. J Clin Oncol. 2014;32(33):3716-3722.
