Dietary trial in prostate cancer: Early experience and implications for clinical trial design

Much epidemiologic and case-controlled evidence suggests that diet may be a modifier of prostate cancer risk. However, the role of dietary modification in men known to have prostate cancer is a matter of some debate. To elucidate the effect of diet and comprehensive lifestyle changes on cancer risk, we are conducting a randomized, prospective clinical trial on men with clinically localized prostate cancer who have selected "watchful waiting" as primary therapy. Since its inception in April 1997, 93 men have been randomized to control (n = 47) or dietary and lifestyle intervention (n = 46). Patients in the intervention group are asked to eat a low-fat, soy-supplemented vegan diet and take part in stress management, psychosocial group support, and exercise programs. After 1 year, adherence to all four interventions was greater than 80%, and no deaths or adverse outcomes have occurred. To date, we have collected prostate-specific antigen and endorectal magnetic resonance imaging and spectroscopy data on 63 patients (34 control and 29 intervention). This study demonstrates that a randomized, prospective dietary trial for men with localized prostate cancer is safe and feasible. The methodologies used provide insights into practical aspects of diet design and compliance assessment that may be useful templates for future dietary trials.