Media misrepresentation, diet, and prostate cancer

There’s a new diet and prostate cancer story “doing the rounds” in the media. It started out stating that dietary changes can induce “substantial” effects on PSA doubling times among men who have received first-line treatment for prostate cancer. The problem with the story is that is based on a small pilot study published last December, and it fails to point out a number of very important caveats.

Before you read what follows, The “New” Prostate Cancer InfoLink would like to make something extremely clear. If you have a consistently rising PSA following first line treatment (of any type) for supposedly localized prostate cancer, then your first line treatment was not completely successful. You either have progressive disease or at best there are still living prostate cells (that are not necessarily cancerous) within the area treated. If you are sufficiently old or you have a sufficiently short life expectancy, this may not be a big deal, because you may die before the cancer starts to impact your life expectancy or the quality of your life. For other younger or healthier men, the situation is not the same at all.

Dietary change alone may have some impact on your PSA without necessarily affecting your risk for progressive disease. We have known for 60 years that hormone therapy can lower a prostate cancer patient’s PSA to zero, but we still do not know (definitively) that hormone therapy has any impact on overall long-term survival. It has long been suspected that dietary change may be capable of a similar effect (without the side effects of hormone therapy) in at least some men.

The original study by Carmody et al. appeared in Urology last December. The “New” Prostate Cancer InfoLink didn’t comment on it at the time because it was such a small study and none of its results were statistically significant (which Carmody et al. were very clear about).

The study was set up to determine whether men who had received first-line treatment for prostate cancer could make a change to a diet emphasizing plant-based foods and fish that would have impact on their quality of life (QoL) and their PSA velocity post-treatment.

A total of 36 men and their partners were randomly assigned to attend a series of 11 dietary and cooking classes that also integrated so-called “mindfulness practice” as a support in making the change or a wait-list control group. The study assessed dietary intake, QoL, and PSA at baseline, after intervention (11 weeks), and 3 months after intervention. In other words, this study is based on the idea of dietary change in just 18 prostate cancer patients over a very short time frame. It was a pilot study.

The authors reported the results of the study as follows (and we have been very careful to use their precise words:

  • “The intervention group showed significant reductions in the consumption of saturated fat and increased consumption of vegetable proteins with accompanying reductions in animal proteins, including dairy products.”
  • The intervention group also “showed increased QoL.”
  • There was “no significant change … in the rate of PSA increase between the two groups.” However, “the mean PSA doubling time for the intervention group was substantially longer at the 3-month follow-up visit than that of the controls.”

Carmody and colleagues concluded that, “Men with a increasing PSA level after primary treatment were able to make a change to a prostate-healthy diet, accompanied by increases in QOL. No significant difference was found in the log PSA slope between the two groups; however, the PSA doubling time increased substantially in the intervention group compared with that in the controls. Future trials should examine the effect of the prostate-healthy diet with a larger sample of men for a longer period.”

Now let’s look at how this information got “re-packaged” in a Reuters Health story yesterday, under the heading, “Low-fat, vegetarian diet slows PSA doubling time”. The first paragraph of the story read as follows:

A diet low in saturated fat, high in vegetable protein and low in animal protein, including dairy products, is associated with a “substantial” [de]crease in prostate-specific antigen (PSA) doubling time and an increase in quality of life, according to results of a pilot study.

[Editorial coment: The story actually uses the words, “increase in prostate specific antigen (PSA) doubling time” but they clearly meant “decrease.”]

In other words, by immediately (and accurately) quoting the study result and emphasizing the words vegetarian (in the headline) and substantial (through the use of the quotation marks), Reuters Health has raised the implicit suggestion that this diet (which was not in fact vegetarian at all) has a statistically significant impact on PSA doubling time, which it clearly did not according to Carmody et al.

By the time this story had reached the AHIP Solutions SmartBrief the headline read, “Lower prostate cancer risk seen with low-fat diet.” What is AHIP? I quote:

America’s Health Insurance Plans (AHIP) is the national association representing nearly 1,300 member companies providing health insurance coverage to more than 200 million Americans. Our member companies offer medical insurance, long-term care insurance, disability income insurance, dental insurance, supplemental insurance, stop-loss insurance and reinsurance to consumers, employers and public purchasers.

In other words, the Reuters Health story had managed to turn a very honest report by Carmody et al. into a signal to the US health insurance industry that a rising PSA after first line treatment was potentially manageable through dietary intervention.

Do I think anyone did any of this deliberately. Sadly, no, I don’t. I think that at least one “journalist” who was under-informed about his or her subject matter mistakenly represented the facts originally presented by Carmody et al. (After all, they couldn’t even get right the fact that the dietary change decreased PSA doubling time as opposed to increasing it.) I suspect that Reuters Health “needed a story,” sent a junior staff member off to “find one,” and that its “fact checkers” didn’t do a good job of checking the facts!

Just so that we are clear about it, The “New” Prostate Cancer InfoLink has long understood that dietary change can impact rising PSA levels (both before and after first or second or even third line treatment) in patients with prostate cancer. How? Well, for starters, it is certainly possible that a low-fat diet that is higher in vegetable proteins may lead to increases in the levels of natural LH and LHRH in your body, which would lead to greater feedback control over testosterone levels and therefore a “hormone-like” impact on prostate cancer development. And that’s just one possibility among many! A second is that those of us who live in America and who cut down on our intake of meat and dairy products (replacing them with vegetable proteins) may be reducing the impact of hormones used on animals in the meat and dairy industry over decades.

Whatever … We could all improve our diets, and potentially our life expectancy, by eating better and dropping a few pounds (the current author included). However, dietary change of this type is utterly unknown to have an overall survival benefit on men with a prior diagnosis of prostate cancer. … And Reuters Health should have known better!

2 Responses

  1. Mike,

    You are making several assumptions that are misleading. I know the people at SmartBrief. They are basically a newsclipping service for newsletters for various industries. Are you saying that this article was inappropriate for their newsletter?

  2. Kathy:

    Reuters Health didn’t write the headline that appears in the AHIP Solutions SmartBrief e-newsletter, SmartBrief did. I don’t think I am making any “assumptions” at all. What I am saying is that the heading and the text on the article in the AHIP version of SmartBrief is a misrepresentation of the original scientific work. The many thousands of health insurance industry executives who read this report will be potentially misled by it as a consequence of the original Reuters Health report and the way that report is presented by SmartBrief. Are you suggesting that publishers of media services like Reuters Health and SmartBrief don’t have any responsibility for the accuracy of what they disseminate?

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