Purpose: Cancer is a major cause of mortality and morbidity throughout the world, and ranks as the second leading cause of death in the United States. Most cancers have a latent period of 10 to 20 years, which provides ample time for preventive measures. Transitional cell carcinoma of the bladder and adenocarcinoma of the prostate have protracted courses and may be ideal for chemopreventive strategies. We review the biochemistry and epidemiology of chemopreventive agents, and the laboratory and clinical studies of their role in urological cancer.
Materials and methods: We performed a computerized MEDLINE search and manual bibliographical review of relevant peer reviewed studies and reports from 1966 to 1998. These reports were analyzed and scrutinized, and the important findings are summarized.
Results: Neoplastic lesions of the bladder and prostate are uniquely suited to the development and evaluation of chemopreventive agents. Epidemiological reports provide the strongest evidence of a protective role for dietary agents in cancer of the bladder, prostate and kidney. Observational and recent experimental trials support these findings in cases of adenocarcinoma of the prostate and transitional cell carcinoma of the bladder. There is strong evidence for a protective effect of vitamin A in bladder cancer. Superior protection has been reported with a combination of high doses of vitamins A, B6, C and E plus zinc. For prostate cancer strong evidence exists for a preventive effect of reduced fat intake, vitamin E, selenium and soy proteins. A lesser benefit is also suggested with intake of vitamins D and C. Evidence of chemoprevention against renal cell cancer is supported mainly by epidemiological studies, and animal studies indicate possible benefit of vitamin D supplementation.
Conclusions: Although there is no incontrovertible proof, numerous studies implicate dietary and nutritional factors in the onset and progression of cancer of the bladder, prostate and kidney. It is possible that the preventive effect of dietary constituents may be in part from consumption with other nutrients and bioactive compounds in whole foods. Further research is needed before vitamins and other nutritional supplements can be advocated as standard therapy but the preponderance of evidence supports increased intake of vitamins A, B6, C, D and E, reduction of animal fat, and increased consumption of fruits and vegetables.