Initial results of the MEAL trial in men on active surveillance

At the annual meeting of the American Urological Association early this morning in San Francisco, we we given the initial report on the results of the Men’s Eating and Living (MEAL) trial. This trial was designed to test the efficacy of a high-vegetable diet to prevent clinical progression in prostate cancer patients on active surveillance.

Between 2011 and 2015, Parsons et al. randomized nearly 500 men who had been started on active surveillance to a telephone-based, validated diet counseling intervention promoting vegetable intake or to a control arm for a period of 2 years.

All eligible patients had to meet the following study entry criteria:

  • Age between 50 and 80 years
  • Diagnosed with biopsy-proven adenocarcinoma of the prostate
  • Diagnosis within the prior 24 months by prostate biopsy with at least 10 cores, of which < 25 percent of the total number of cores and ≤ 50 percent 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
  • Serum PSA level < 10 ng/ml

Patients were stratified by age (< 70 years vs. ≥ 70 years), by race (African American vs. Other) and by time since diagnostic biopsy (0 to 12 months vs. > 12 and ≤ 24 months).

The primary study outcome was clinical progression, defined as a serum PSA level ≥ 10 ng/mL, a PSA doubling time < 3 years, or pathological progression on follow-up biopsy. The primary endpoint was time to progression (TTP), defined as the length of time from the date of random assignment to clinical progression.

Patients who died from any cause without experiencing progression were censored at the time of death and patients who elected to pursue treatment despite not meeting the criteria for progression were censored at the time of withdrawal.

Here are the study findings:

  • The study enrolled 478 patients at 91 study sites.
    • 237 of these men were randomized to the diet counseling service
    • 241 were randomized to the control arm and received a thorough booklet with introductory information about living with localized prostate cancer
    • 12 percent of the patients were African American.
    • Slightly less than 2 percent of the patients had Gleason 3 + 4 prostate cancer, so this was a truly low-risk population of patients
  • The dietary counseling service clearly did significantly change the diets of the men randomized to this service as compared to the control group
    • These patients ate significantly higher levels of carrots and tomatoes.
    • They also lowered their levels of meat intake over the 2 years of the study
  • However,the change in diet had no significant impact on
    • Risk for prostate cancer progression among the diet counseling group compared to the control group
    • Body mass index (BMI) levels among the diet counseling groups compared to the control group and compared to baseline levels.
  • The numbers of patients in each arm of this trial who transitioned from active surveillance to invasive treatment over the course of this strial was very low indeed — in both arms of the trial

The base result here is that in a well-conducted trial with high patient adherence, change to a “higher vegetable” diet had no impact on risk for prostate cancer progression over a period of 2 years.

It may be that the very low-risk nature of the patients enrolled into this trial already made their risk for disease progression to be so low over a 2-year time frame that dietary change alone over that time frame could not have been sufficient to change their risk level.

15 Responses

  1. Dean Ornish et al. of UCSF were conducting pilot trials of diet and lifestyle on men on active surveillance, begun around year 2000. In the short term, they were seeing modestly favorable results — slowing of PSAV, inclination on the part of patients to feel they could delay aggressive treatment, etc. I’ve been finding their published abstracts on PubMed with a search on: Ornish D and “prostate cancer”.

  2. What’s the point of trying to lower the risk for guys who are already low risk? Wouldn’t it be more meaningful to do a trial on high risk guys? Or would they refuse to participate in something which might lead to dire consequences?

    I’ve always thought that improving diet was meant to lower comorbidities which accompany PCa treatment rather than lower PCa progression anyway.

  3. Dear Charles:

    The data published by Ornish et al. were one of the stimuli for the development and implementation of the MEAL trial. However, if you read the Ornish papers with care what you will find is that the men in his trials had to adhere to lifestyle changes (vegan diet, exercise, and other things) that are unrealistic in the real world; they were very small trials; and there has been no long-term follow-up.

    There may be a small subgroup of very highly motivated men who can “make this work”, but I for one was very disappointed to see that there was no meaningful effect on disease progression in the MEAL trial … and I was sitting in the room when it was presented.

    Much as a I want to believe that diet and exercise can really make a difference in extending time to disease progression and in extending prostate cancer-specific survival, we still have no compelling data to support that belief.

  4. Dear Bob:

    The point of trying to lower risk for progression in men who start out with low-risk disease is to see if we can avoid treating them at all … ever!

    I agree that it is arguable that the MEAL trial should have tried to enroll more men with Gleason 3 + 4 = 7 disease, but most physicians still thought that was too risky when this trial was first designed and started to be implemented.

    I would encourage any man with high-risk disease to eat a healthy diet and to exercise as much as he can manage, but not in a trial like this where that was the only intervention! They should be doing this anyway, but men with high-risk disease need treatment or they are going to die of metastatic prostate cancer (regardless of how much they exercise or how good their diet is).

  5. Very good advice from the Sitemaster, as usual.

  6. I can’t see anything about exclusion of dairy in this trial — other than “healthy diet” — whatever that means. Also find it curious that,as mentioned in one of the comments, in “the real world”, it seems bombarding an already out of balance system with toxic chemicals in order to “help” is deemed logical, whereas supporting it by looking at what unhelpful food intake might be reduced is not?

  7. Dear Bears’s daughter:

    (1) There is no evidence that I am aware of that “exclusion” of diary products has any defined and beneficial effect on the progression of prostate cancer (although excessive intake of dairy and other high-fat products may do).

    (2) None of the patients in this trial were being “bombarded” with any toxic chemicals at all … or any other form of medical treatment. The whole point of this trial was to explore whether a diet high in vegetable products and therefore lower in high-fat products could affect risk for progression of low-risk prostate cancer.

    I am therefore not sure how you comments are of any relevance to these data.

  8. For what it is worth, here are my 2 cents:

    — My prostate cancer is very advanced; Gleason scores of 9 and 10s.
    — Three major cancer centers gave me from 8% to 2% chances of beating it.
    — Couldn’t do surgery — too advanced.
    — Did all the hormone treatments and max. radiation, etc.
    — The Best Med for me has been one word: “NUTS” … taught to me while in training by the 101st Airborne Division, WW II Vets of the Battle of the Bulge: “YOU NEVER EVER GIVE UP”.
    — My advanced prostate cancer is now 17 years old and I have that one word tattooed on my right arm.

    Ken Wooden/”NUTS”



  10. This study is borderline to actually irresponsible and definitely irrelevant. Eating “more” vegetables is not a thing. The danger is people will use this as a license to eat things that are provably and demonstrably bad for you. Notwithstanding the small chance that a strict vegan or plant-based lifestyle can positively affect prostate cancer, the ancillary benefits to an improved metabolism will help give the strength to carry the battle forward. Low-grade cancer studies over the phone seems silly to me. How about doing blood work to see if the numbers are actually improving for the patients’ metabolism. People will lie. Also, urologists do not want to see positive results from anything that will cut in to their income.

  11. This was an extremely well done clinical trial. They did, in fact, do a sample of blood tests to assure compliance. Here is a link to the specs of the study.

    The researchers were actually hoping for proof that the dietary intervention might help men on active surveillance stay on it longer. In the first 2 years it had no effect. There may be many reasons for changing diet — this was so far not one of them.

  12. What I would like to have seen is a scatter plot of individual data. In the age of the internet, that would be trivial. It’s possible that a subgroup experienced a great benefit, yet when their data was blended in with all the rest of the exp group, the benefit is obscured. I say that because of reading a report of great regression (Gleason, PSA, et al.) from a trial subject.

    If more than a few such outliers exist, we could look for what they have in common.

    OTOH, if the controls (pamphlet) group showed a similar percentage of outliers experiencing regression, then we can probably assume it was spontaneous in all outliers.

    There is also this: “The dietary counseling service clearly did significantly change the diets of the men randomized to this service as compared to the control group.”

    Right, but by how much? If the two groups differ by only a small amount of serum phytochemicals, then so what if the difference is statistically significant? Does the sample of ~500 give enough statistical power to detect significance in a small difference between serum values —- yet still fail rightly to show a statistically significant difference in clinical benefit because the dose was too small?

    What I’m thinking here is that large doses of powdered vegetables might work.

    PS: It’s great of you to have posted these initial results, thanks. (I started out by looking to see if perhaps the study had been halted for efficacy… oh well.)

  13. Dear Joints:

    This report provides most of the data actually presented by the principal investigator of the MEAL trial at the AUA annual meeting. I am sure that when the full results are available and published, they will include more detail of the type you are looking for.

    With regard to whether the quantity of change in diet was sufficient to have a clinical impact, one might also want to think about whether the districtly low-risk nature of this group of men and the fact that they were only followed for 2 years may also have limited the chance that even a significant change in their diet would have be in place for long enough to impact their time on active surveillance.

  14. I don’t suppose that you know the P value, right? If it were, say, 0.06 or so, then that would change interpretation a lot — IMO anyway.

  15. Dear Joints:

    I don’t remember the author reporting any detailed statistical data … but he was very clear that it was not statistically significant with regard to any impact on whether patients did or did not stay on active surveillance.

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