The United States Preventive Services Task Force has moved on from ambivalence about prostate cancer screening with the PSA test, and inveighed decisively against it. As is ever the case with guidance about cancer screening, this recommendation is apt to stoke the flames of competing passions, and generate a whole lot of heat but altogether too little light.
To defend against that, let's try to keep our passions in check and appraise the relevant elements of this recommendation analytically and see where we land. Those elements include: (1) the nature of the USPSTF and its work, (2) the nature of prostate cancer, (3) the nature of screening tests in general, (4) the nature of evidence, and finally, (5) the nature of the nature/nurture debate and its pertinence to prostate cancer screening.
(1) The USPSTF can certainly be trusted. This is a multidisciplinary group of experts in preventive medicine, evidence review, clinical medicine, and public health practice. They are convened by federal agencies -- notably the Agency for Healthcare Research and Quality (AHRQ) -- but are independent of them. The sole job of the task force is to review the current evidence, and reach conclusions about it.
A unique feature of this group is that while they do have skin in the game of evidence-based recommendations, they have no skin in the game of clinical care that ensues. In other words, members of the task force don't lose or win if we do, or don't, screen for prostate cancer. They have no stake in the use of any particular test or technology.
That is not true of the many groups that often respond critically to task force recommendations for doing less. Cardiologists have a stake in echocardiograms. Gastroenterologists have a stake in endoscopy. And cancer societies have a stake in doing more, not less, about cancer.
Often, those groups are the ones who use the test or technology in question, and doubtless believe in it -- and profit from it. The American Urological Association was quick to point out the liabilities in the task force process, and the fallacies in its conclusion. But the urologists have skin in this game, and thus a conflict that the task force lacks.
What the task force lacks, though is wiggle room. They are boxed in by the high standards of their evidence review, and really have no allowance for informed conjecture about how things might be done better. They evaluate what we are doing, based on studies already completed. Where that can fall short is addressed in point number four, below.
(2) Prostate cancer is unpredictable. Most men who die after age 80 die with it, but not of it. Finding those cases that are destined to remain localized and inconsequential, and not recognizing them as such, will tend to result in a "cure" far worse than the indolent disease. But, of course, other cases do progress, spread, and can prove lethal. The unpredictability of prostate cancer and the limits of our current prognostic abilities make it tough to confer consistent benefit when disease is found early.
(3) Screening is applied to the general population -- and is, literally, looking for trouble. To find it whenever it's there, you need a test that is very sensitive -- but such tests tend to produce false positives. If you want to avoid a lot of false positives, you need a test that's very specific -- but then you tend to miss some cases of actual disease. For these reasons, screening is not invariably a good idea; just because we can, doesn't mean we should. The test performance, predictability of the disease, prevalence of the condition, and capacity to intervene effectively when disease is found early all factor in.
(4) Evidence is one of those areas where, to quote Mick Jagger, you can't always get what you want. We are often awaiting more data, better studies, longer follow-up. While waiting, the task force often concludes it cannot conclude anything -- and recommends neither for nor against a particular test. In the case of PSA testing, they are recommending against its use based on the evidence we have now -- which is, in turn, based on the kind of screening we now do. This does not mean there aren't ways to screen for prostate cancer that would confer net benefit; it just means we haven't settled on them yet. Maybe they aren't worked out; maybe they are too expensive. In the case of our current methods, we have evidence of absence of a beneficial effect. In terms of alternative approaches to screening that are in development, we have something very different: absence of evidence. That means recommendations can, and should, be revisited as new evidence comes in. A task force recommendation is for now -- not forever.
(5) And finally, there's the issue of what we can do while we are not being screened for prostate cancer. Here, I think it's important to recall that screening does not PREVENT cancer; it just finds it early, which may help prevent it from advancing. Preventing it outright is better.
And we do have evidence that a short list of lifestyle factors can help prevent prostate cancer, and prevent it from progressing once it has developed. A 2008 study, for example, showed that a lifestyle program incorporating the usual elements -- avoidance of toxins like tobacco, an optimal mostly-plant-based diet, regular physical activity, stress management, adequate sleep, good social interactions (I call these "feet, forks, fingers, sleep, stress & love") -- dramatically down-regulated cancer promoter genes, and up-regulated cancer suppressor genes in men with early-stage prostate cancer.
We can do better than just watch and wait during the period of "watchful waiting" -- we can nurture nature, and change the inner world of our genes.
There will no doubt be better ways to screen for prostate cancer in the future -- ways that meet the USPSTF standard. While waiting for the advent of better methods, I am a 49-year-old male, and do not get screened. In contrast, I certainly will get colonoscopy next year, for which the evidence is decisively good.
But I am not just leaving the fate of my prostate to chance while hoping better screening methods come along. I am using the power of lifestyle to nurture whatever predispositions nature dealt me, and reshuffle the deck in my favor. You don't need an invitation from the USPSTF to do likewise.
-fin
Dr. David L. Katz; www.davidkatzmd.com
www.turnthetidefoundation.org
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