Increased vegetable intake not linked with reduced PCa progression

February 3, 2020

Eating more vegetables will not alter the natural history of prostate cancer or otherwise prevent progression of localized disease, according to a recent study.

A behavioral intervention can successfully motivate men with early-stage prostate cancer to modify their diet by increasing vegetable consumption. Eating more vegetables, however, will not alter the natural history of prostate cancer or otherwise prevent progression of localized disease, according to the results of the prospective Men’s EAting and Living (MEAL) Study.

Published in JAMA (2020; 323:140-8), the study was conducted through the Cancer and Leukemia Group B. It randomized 478 men who were being managed with active surveillance for early-stage prostate cancer to receive either behavioral intervention counseling that encouraged consumption of ≥7 fruit or vegetable servings per day or written information about diet and prostate cancer. Men were followed for 24 months post-randomization.

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Dietary data and measurement of plasma carotenoids indicated that the behavioral intervention was effective for increasing intake of vegetables, cruciferous vegetables, and carotenoids. However, there were no statistically significant differences between the intervention and control groups in the primary outcome that assessed time to progression (adjusted hazard ratio, 0.97 [95% confidence interval, 0.76 to 1.25]) or in the prespecified secondary outcome comparing the intervention and control groups for total number [percentage] of patients who pursued active treatment during follow-up without meeting protocol-defined progression criteria (6 [2.7%] vs. 4 [1.8%]; p=.75). The hazard ratio for time to treatment was also not statistically significant.

Lead author J. Kellogg Parsons, MD, MHS, told Urology Times, “The prostate cancer survivorship care guideline from the American Society of Clinical Oncology and the Prostate Cancer Foundation endorse increased consumption of vegetables to improve outcomes for prostate cancer survivors, but these recommendations are based on expert opinion and findings from preclinical and observational studies. We believe ours is the first randomized controlled trial investigating a dietary intervention for prostate cancer, and in contrast to prevailing scientific and public opinion, our study’s findings do not support increasing vegetable intake to decrease prostate cancer progression in men with early-stage disease who are being managed with active surveillance.”

Next: “Our study did prove for the first time that a simple and inexpensive intervention program could change men’s diets for the better."“Our study did prove for the first time that a simple and inexpensive intervention program could change men’s diets for the better. Diet and other behavior modifications, such as exercise, are still endeavors worth considering-particularly in patients with metastatic prostate cancer. For example, promoting general health through better diet may have a particular benefit for improving tolerability of cancer treatments, such as androgen deprivation therapy,” added Dr. Parsons, of the University of California, San Diego.

Participants for the MEAL study were enrolled at 91 urology and medical oncology clinics across the United States. Eligible patients were aged 50 to 80 years who had been diagnosed within the previous 24 months with stage ≤cT2a biopsy-proven prostate cancer and serum PSA ≤10 ng/mL. Men aged <70 years were required to have International Society of Urological Pathology grade group 1 (Gleason score 3+3=6) cancer and older men had to have been classified as having group 2 (Gleason score ≤3+4=7) or less cancer. All men had to be treatment naïve and be consuming <6 servings per day of fruits and vegetables.

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Counseling on diet was done remotely through the UC San Diego Moores Comprehensive Cancer Center by trained counselors who contacted men by telephone throughout the duration of the study. The counseling encouraged eating ≥7 servings per day of fruits and/or vegetables, including ≥2 servings of cruciferous vegetables or tomatoes. The control group received printed materials from the Prostate Cancer Foundation encouraging vegetable consumption.

For the outcome analysis, time to progression was defined as the length of time from the date of randomization to PSA level of ≥10 ng/mL, PSA doubling time <3 years, or pathologic progression on follow-up biopsy. At the end of the study, prostate cancer progression occurred in 124 men in the intervention group and in 121 controls. The 24-month Kaplan-Meier progression-free percentages were 32.5% in the intervention group and 41.4% in the control group.