THE POTENTIAL FOR HORMONAL PREVENTION TRIALS

Breast and prostate cancer are significant causes of morbidity and mor tality and are very similar in etiology, epidemiology, and modalities of treatment. Investigational strategies in the prevention of these ma lignancies also have strong parallels. The National Cancer Institute i s sponsoring several large scale clinical trials involving hormonal ma nipulation and cancer prevention. In the Breast Cancer Prevention Tria l, 16,000 women at high risk for breast cancer are being randomized to receive the antiestrogen agent tamoxifen or placebo for 5 years in an effort to determine if breast cancer development can be inhibited. In a similar trial, the Prostate Cancer Prevention Trial, 18,000 men old er than 55 years of age will be randomized to receive finasteride, a 5 -alpha-reductase inhibitor, or placebo to determine if inhibition of d ihydrotestosterone synthesis in the prostate over a prolonged period w ill lead to a decreased incidence of prostate cancer. Both clinical tr ials offer the possibility of demonstrating that a hormonal interventi on can decrease an individual's risk of developing breast or prostate cancer. They also have the potential of providing critical information about cancer risk, etiology, screening, and genetics, as well as quan tifying the risks and benefits of specific preventive interventions.