Increased vegetable consumption does not decrease prostate cancer progression

Reference

Parsons JK, Zahrieh D, Mohler JL, et al. Effect of a behavioral intervention to increase vegetable consumption on cancer progression among men with early-stage prostate cancer. The MEAL randomized clinical trial. JAMA 2020;323(2):140-148.

Synopsis

Current recommendations widely circulated in the public domain encourage the consumption of diets high in vegetables to reduce the risk of disease progression in patients with early-stage prostate cancer. These investigators identified men, aged 50 to 80 years, with early-stage prostate cancer based on standard international diagnostic criteria and managed with active surveillance. Eligible patients (N = 443) randomly received assignment (concealed allocation) to either a telephone-based counseling intervention or a usual-care control group. Intervention participants were assigned to a counselor who encouraged the consumption of a diet high in leafy green, carotenoid, and cruciferous vegetables through 16 regularly scheduled counseling telephone calls over a 2-year period. Control participants received printed materials encouraging consumption of a vegetable-rich diet. Prostate-specific antigen (PSA) testing occurred every 3 months, starting at baseline, and participants who did not meet the criteria for additional cancer treatment underwent an end-of-study biopsy at 24 months. The study was at least 80% powered to detect a predetermined clinically meaningful 10% group difference in cancer progression rates. Intervention participants reported a significant increase in daily total vegetable servings compared with controls. Plasma carotenoids measured at 12 months in a random of sample of participants validated self-reported dietary data. Using both per-protocol and intention-to-treat analyses, no significant group differences occurred in the primary outcome of PSA level of 10 ng/mL or greater, PSA doubling time of less than 3 years, or upgrading of either tumor volume or grade on follow-up prostate biopsy.