Diet & Prostate Cancer: Mixed Results

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A decade ago, J Kellogg Parsons, MD and colleagues published their pilot trial of the Men’s Eating and Living (MEAL) study, assessing the feasibility of implementing a diet-based intervention in men with prostate cancer.

• Among 74 men aged 50-80 were randomized to receive either telephone-based dietary counseling or standardize, written nutritional information.
• In the intervention arm, the mean daily intakes of total vegetables, crucifers, tomato products, and beans/legumes increased by 76%, 143%, 292%, and 95%, respectively, whereas fat intake decreased by 12% (p = 0.02).
• According to the American Psychological Association, counseling is grounded in social psychology: promoting a capacity to execute behaviors to produce specific performance attainments.

Recently, Parsons and colleagues presented results of their phase III Meal study, testing the efficacy of a high-vegetable diet to prevent clinical progression in prostate cancer patients on active surveillance.

• In this phase III trial, men were randomized 1:1 to a telephone-based, validated diet counseling intervention promoting vegetable intake or to a control condition for two years. The goal of the intervention arm was ≥7 servings/day of vegetables (with an emphasis on raw carotenoids – tomatoes and carrots). Key inclusion criteria for this study included:
  • Age 50 to 80 years
  • Biopsy-proven adenocarcinoma of the prostate
  • Diagnosis ≤ 24 months prior to presentation with ≥ 10-core prostate biopsy in which < 25% of the total number of cores and ≤ 50% of any single core contained cancer
  • Gleason sum ≤ 6 for men ≤ 70 years and Gleason sum ≤ (3 + 4) = 7 for men > 70 years
  • Clinical stage ≤ T2a

• From 2011 to 2015, there were 602 patients screened for the trial, enrolling 478 (103%) of a targeted 464 patients.
• At 91 study sites, 237 men were randomized to telephone counseling (intervention) and 241 to the Prostate Cancer Foundation booklet (control).
• At baseline, the mean age was 64 (SD 6) years, mean PSA was 4.9 (SD 2.1) ng/mL, and 56 (12%) participants were African-American.
• The total vegetable servings per day increased at both 12 and 24 months for the intervention vs control group (p<0.001), with similar findings for lycopenes (p<0.001), and plasma carotenoids (p=0.01 at 12 months, p=0.08 at 24 months). Interestingly, fat calories significantly decreased in the intervention arm vs the control arm at both 12 and 24 months (p=0.02).

There was no difference between the dietary intervention arm vs the control arm with regards to the primary outcome of time to progression (HR 0.96, 95%CI 0.75-1.24). Furthermore, there was no difference in PSA specific endpoints (PSA >10 ng/mL or PSADT < 3 years) (HR 0.86, 95%CI 0.65-1.13). Time to treatment rates (surgery or radiation) were comparable between the two groups: 2.7% for dietary intervention vs 1.8% for the control group (p=0.61).

Parsons concluded by highlighting that this trial is the first successful, sustainable behavior intervention in prostate cancer, despite no significant effect on two-year clinical progression among men on active surveillance for prostate cancer. Several other take home messages from his presentation include:

• Large-scale diet change in prostate cancer is feasible.
• No effect is seen on shorter term clinical progression.
• Longer term effects remain unclear.

"AUA 2018: The Men’s Eating and Living (MEAL) Study: A Randomized Clinical Trial of a Diet Intervention in Men on Active Surveillance for Prostate Cancer," UroToday, 2018, https://www.urotoday.com/conference...-active-surveillance-for-prostate-cancer.html