A follow-up on active surveillance and the MEAL study


A couple of weeks ago, the full report on the Men’s Eating and Living (MEAL) study was published in the Journal of the American Medical Association. It has generated a lot of discussion, some of which is distinctly misguided. We would remind readers that the initial report on the results of this study was presented by Parsons and his colleagues nearly 2 years ago, at the annual meeting of the American Urology Association in San Francisco in May 2018. We had provided a detailed assessment of the study at that time. It’s worth re-reading.

The bottom line is that in a randomized controlled trial that enrolled exclusively men with low- and very low-risk forms of prostate cancer who were being managed on active surveillance, a diet high in vegetables, which one group of patients were encouraged to eat through a carefully structured telephone outreach program, did not improve the rates of disease progression or the rates of prostate cancer-specific survival of these patients over a period of 2 years.

Should we be surprised by this result? Your sitemaster doesn’t think so. Here are some of the reasons why:

  • The patients enrolled into this trial were at distinctly low risk for progression of their cancer at all. They all met at least the criteria for low-risk prostate cancer.
  • The patients who were randomized to the group encouraged to eat a diet high in vegetables were then monitored for just 2 years … which is a very short period of time.
  • The authors themselves write that “the study may have been underpowered to identify a clinically important difference.”

We tend to have unreasonable expectations of how relatively short-term changes in our lifestyles (diet, exercise, etc.) may affect our overall state of health. If one has been eating a “standard” western diet for most of the past 50 years (which most of the men in this trial probably had), and then you change to a diet high in vegetables for just 2 years, it is hard for your sitemaster to see why this might have made much of a difference to the key outcome in this trial, which was time to disease progression, where progression was defined as any one or more of the following:

  • A PSA level that rose to 10 ng/ml or greater
  • A PSA doubling time of less than 3 years
  • Upgrading (defined as increase in tumor volume or grade) on follow-up prostate biopsy

Your sitemaster is of the entirely personal opinion that the patients enrolled in the MEAL trial would need to have been followed for at least 5 years before we might have reasonably expected to see any sort of difference in outcome between the two groups of patients — and 10 years would have been better.

The authors of the MEAL trial manage to conclude that:

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. The findings do not support use of this intervention to decrease prostate cancer progression in this population, …

However, your sitemaster doesn’t think this is a reasonable conclusion. He thinks that the following would have been a much more accurate and reasonable conclusion:

Among men with early-stage, low- and very low-risk prostate cancer managed with active surveillance, a behavioral intervention that increased vegetable consumption did not significantly reduce the risk of prostate cancer progression at 2 years of follow-up. The findings do not support use of this intervention to decrease prostate cancer progression in this population over such a short time period, …

There remain multiple reasons to believe that changes to lifestyle over significant periods of time may have all sorts of impact on both risk for prostate cancer at all and on the progression of prostate cancer over time once diagnosed. The data from the MEAL trial merely show us that if you study this in a group of men who are at low risk for progression to begin with, you are unlikely to see any effect in as little of 2 years. We shouldn’t be throwing out the baby with the bathwater.

 

6 Responses

  1. It’s a good idea in any event to eat a lot of vegetables.

  2. Indeed … for all sorts of reasons, particularly cardiovascular and gastrointestinal ones.

  3. I was frustrated as well by the findings of this study for the same reasons you raised. Thanks for being the voice of reason, again.

  4. Best advice on diet: Eat food, mostly plants, not too much. Food, in this descriptor, means closest to origin and not highly processed, treated, salted, advertised “snacks”, candy, and so on.

  5. The supplements astaxanthin or vitamin D3 may prevent prostate cancer from becoming aggressive. Melatonin may also be of use (see here).

  6. The value of these supplements and of melatonin in the management of prostate cancer remains unproven. While many men use many different supplements in the hope that they may be able to control progression of their disease (or to prevent the disease entirely), the data supporting such strategies is extremely limited and so patients would be wise to limit their expectations.

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