Update on prostate cancer chemoprevention

Abstract

Background: Prostate cancer is the most common type of cancer and the second leading cause of cancer-related deaths in American men. Its high rate of occurrence and long lead time to clinically significant disease make prostate cancer an ideal disease for pharmacologic or nutritional chemoprevention.

Methods: To identify the various chemoprevention strategies for prostate cancer, a MEDLINE search (from 1967-2005) and bibliographic search of the English-language literature were conducted.

Results: Epidemiologic and retrospective studies have assessed the effect of carotenoids (e.g., lycopene), vitamins, selenium, and nonsteroidal antiinflammatory drugs (NSAIDs) on the rate of occurrence of prostate cancer. The few published prospective trials evaluated prostate cancer as a secondary end point. Lycopene (as beta-carotene) and selenium supplementation have been associated with a reduced risk of prostate cancer in nested case-control studies, but only in subgroups of men with low baseline plasma lycopene (or beta-carotene) and selenium levels respectively. The Prostate Cancer Prevention Trial prospectively evaluated finasteride, a 5-alpha-reductase inhibitor, as chemoprevention. The results showed a 25% relative risk reduction in prostate cancer, albeit at an increased risk of invasive tumors.

Conclusion: Data regarding lycopene, vitamin E, and selenium as chemoprevention for prostate cancer appear promising. Prospective trials such as the Selenium and Vitamin E Cancer Prevention Trial (SELECT) will clarify the role of these agents in prostate cancer prevention. The role of NSAIDs is unclear, and the long-term toxicity associated with NSAIDs may limit their usefulness. Although finasteride has decreased overall prostate cancer occurrence, the risk of invasive tumors may outweigh the benefit of this agent. The continuing Reduction by Dutasteride of Prostate Cancer Events (REDUCE) trial may help define a role for the 5-alpha-reductase inhibitors in cancer chemoprevention. At this time, nothing has been proven effective as chemoprevention against clinically significant prostate cancer.