A randomized trial observed no association between increased vegetable intake and reduced cancer progression in patients with early-stage prostate cancer.
“Guidelines endorsing vegetable-enriched diets to improve outcomes for prostate cancer survivors are based on expert opinion, preclinical studies, and observational data,” explained the study authors, whose research was published in JAMA.
The trial was the Men’s Eating and Living (MEAL) study, a randomized clinical trial spanning 91 urology and medical oncology clinics in the U.S. A total of 478 men aged between 50 and 80 years were enrolled. Patients were eligible for inclusion if they had biopsy-proven prostate adenocarcinoma (International Society of Urological Pathology grade group = 1 in those <70 years and ≤2 in those ≥70 years), stage cT2a or less, and serum prostate-specific antigen (PSA) level less than 10 ng/mL. Patients were enrolled between January 2011 and August 2015, and follow-up took place between January 2013 and August 2017. Patients were randomized to one of two groups. The intervention group received behavioral counseling via telephone promoting the consumption of at least seven daily vegetable servings (MEAL intervention; n=237). The second group received written information regarding diet and prostate cancer (control; n=241). The main outcome was time to progression. Progression was defined as PSA level of 10 ng/m or greater, PSA doubling time of less than three years; or increase in tumor volume or grade on follow-up prostate biopsy.
Of 478 total randomized patients (mean [SD] age, 64  years; mean [SD] PSA level, 4.9 [2.1] ng/mL), the primary analysis included 443 (93%). The MEAL intervention and control groups had similar instances of progression events (124 vs. 121, respectively). Time to progression did not differ between the groups (unadjusted hazard ratio [HR]=0.96; 95% confidence interval [CI], 0.75–1.24]; adjusted HR=0.97; 95% CI, 0.76–1.25]). The 24-month Kaplan-Meier progression-free percentage was 43.5% (95% CI, 36.5–50.6%) for the MEAL intervention group and 41.4% (95%CI, 34.3–48.7%) for the control group (difference, 2.1%; 95% CI, –8.1 to 12.2%).
“Among men with early-stage prostate cancer managed with active surveillance, a behavioral intervention that increased vegetable consumption did not significantly reduce the risk of prostate cancer progression,” concluded the researchers. “The findings do not support use of this intervention to decrease prostate cancer progression in this population, although the study may have been underpowered to identify a clinically important difference.”