SAN FRANCISCO — Adopting a diet heavy with vegetables did not slow prostate cancer progression among men with low-risk disease who were on active surveillance, according to final, 2-year results from a novel US study presented here at the American Urological Association (AUA) 2018 Annual Meeting.
The Men’s Eating and Living (MEAL) study is the first multi-institutional, randomized phase 3 clinical trial of a diet intervention for prostate cancer, said lead author J. Kellogg Parsons, MD, of the University of California, San Diego (UCSD).
But those hopes were not realized, at least in the short term.
“There was no significant effect on 2-year clinical progression in active surveillance,” Parsons told a packed audience at the plenary session.
Specifically, disease progression — the study‘s primary outcome — was roughly the same for the men in the intervention arm (n = 226) as for the men in control arm (n = 217) (hazard ratio, 0.96; P = .76). In the control arm, men were given the Prostate Cancer Foundation’s exercise and nutrition booklet but did not receive specific counseling.
Steven Freedland, MD, of Cedars–Sinai Medical Center, Los Angeles, California, congratulated the MEAL team for undertaking the study. “A healthy diet will reduce inflammation,” he told Medscape Medical News. He explained that vegetables such as broccoli have been found to have an anti-inflammatory effect.
He said that using PSA as part of the disease progression endpoint is tricky. “Elevated PSA in men with low-risk prostate cancer who are on active surveillance may simply reflect inflammation of the gland and not cancer burden. Therefore, you can have a drop in PSA but no real drop in cancer burden,” he told Medscape Medical News at the meeting.
Parsons accented the positive in his presentation. “This is the first successful, sustainable behavior intervention in prostate cancer,” he said. “A large-scale diet change in prostate cancer…is feasible.”
The MEAL study took those findings to the next level — a multicenter, randomized-controlled trial. The scope was national, with 91 sites enrolling patients. The intervention involved the counseling of patients by trained, certified dietitians through a call center at UCSD. “Rather than having the patients come to us, we’d go to the patients [via the telephone],” Parsons said. The goal was to increase daily vegetable intake to seven servings, with a serving being roughly equivalent to a cup of vegetables.
The diet counseling worked. At baseline, men in both groups ate a median of about three servings of vegetables a day. However, at 12 months, the men who received the intervention were eating about six servings daily. By contrast, the patients in the control group were eating only four daily servings. At 24 months, the men who received the intervention had backslid a bit and were consuming a median of five servings; the control patients were eating fewer than four.
“What happens when you increase vegetables is that there is a decrease in all the things that are bad for you, including carbohydrates,” said Parsons
As noted above, the disease progression endpoint included PSA levels, which were similar between the arms. The treatment rates were “surprisingly low,” said Parsons, and were not significantly different. Only 2.7% of the intervention group and 1.8% of the control group underwent surgery or radiotherapy during the 2-year study period.
The MEAL study has attracted a lot of attention in the urology community. In March, eminent researcher and clinician Laurence Klotz, MD, from the Sunnybrook Health Sciences Center, Toronto, Canada, published an essay on MEAL in which he placed it in historical context relating to prevention studies.
“Many epidemiological studies have pointed to the beneﬁts of fruit and vegetable intake high in vitamin E, selenium, beta carotene, lycopene, and other micronutrients, and a diet low in animal fat,” Klotz wrote.
However, “several pivotal studies have taken the bloom off the rose of prevention,” he said. He highlighted the SELECT trial, which found not only that there was no benefit to supplements but also that supplements actually increased the risk of developing prostate cancer.
There have been inconsistent results from studies that examined the association between fruit and vegetable consumption and prostate cancer. As an example, Klotz cited a large observational study of more than 130,000 men that found no signiﬁcant association between fruit and vegetable intake, including consumption of cruciferous vegetables, and prostate cancer (Int J Cancer. 2004;109:119-24).
Despite negative studies, “a lingering spark of hope exists that the many positive population, epidemiological, and preclinical studies supporting dietary approaches to prevention will be vindicated,” said Klotz. “The MEAL study…is, therefore, a laudable and ambitious initiative.”
The study was supported by the National Cancer Institute, the Department of Defense, and the Prostate Cancer Foundation. The authors, Dr Freedland, and Dr Klotz have disclosed no relevant financial relationships.
American Urological Association (AUA) 2018 Annual Meeting. Abstract LBA19, presented May 21, 2018.
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