Tuesday, February 28, 2012

Rethinking shared decisions in prostate cancer screening

Last October, the U.S. Preventive Services Task Force provisionally recommended against screening for prostate cancer using the prostate-specific antigen (PSA) test, eliciting a variety of reactions from medical and patient advocacy groups. The New England Journal of Medicine published one of the most thoughtful responses by Mary McNaughton-Collins and Michael Barry, two physicians who have done a great deal of research on the psychological and physical harms related to false-positive tests, an all-too-common occurrence in men who receive periodic PSA testing. They respectfully disagreed with the USPSTF's "D" (don't do) rating for this preventive service, arguing that the rating should have instead been a "C" (don't do routinely):

A grade C recommendation would allow the patient to be involved in the decision to skip or choose a PSA screening test, after a discussion with a primary care provider about the magnitude of the known harms and the potential for some benefit. The patient could then provide his perspective on how he views the trade-off. Weighing the pros and cons to make a decision about PSA screening is an individual process, and different well-informed men will make different decisions. A grade D recommendation removes the patient from the equation and puts the physician in the central position of discouraging use of the test. Uncertainty in medicine is more common than we usually let on, and the way to address uncertainty is to allow patients the central position in decision making. ... We do not believe that anyone but the patient should decide whether the small and uncertain benefits of PSA screening are worth it.

In 2010, the American Cancer Society took a similar stance, recommending that men age 50 years or older make "informed choices" about whether or not to receive the PSA test after being provided with detailed information about the risks and benefits and tools to help them make the decision. On the surface, both of these recommendations seem more reasonable that the USPSTF's. Rather than making a unilateral decision for every patient based on imperfect population-level evidence, why not let each patient make the choice for himself?

The answer is that primary care physicians have already been trying this approach for many years, and it does not work. Numerous studies have shown that no matter how much information men are given in any format, the vast majority still choose to receive the test, and most of them end up worse off because of that decision. In fact, as a new study concludes in the Archives of Internal Medicine, once prostate cancer is diagnosed via PSA testing, the men most likely to receive aggressive ("curative") treatments are those who are least likely to need it - men who would have been better off not getting the test in the first place.

A case in point: in the same issue of the journal, an academic oncologist who exclusively cares for prostate cancer patients tells the story of his own concerning PSA test, prostate biopsy, and subsequent decision to undergo radical prostatectomy at age 56. Five years later, he is cancer-free, but has permanent right-sided weakness as the result of the surgery, which was in retrospect unnecessary given the limited spread and good prognosis of his tumor. He laments: "Even the most informed patient (me in this case) has difficulty making a truly informed decision." And if a physician who spent decades caring for patients with prostate cancer has trouble making the right call, what hope is there for the rest of us?

Physician-researcher H. Gilbert Welch (author of Overdiagnosed, previously reviewed on this blog) recently challenged the consensus that informed decision-making is the best approach to PSA testing:

I worry that excessive fealty to informed decision-making in cancer screening may distract us from more important issues—like what is bothering patients right now. It may also lead physicians to abdicate our role as advisor—physicians simply transfer responsibility to their patients. And the problem appears to be asymmetric: we seem less inclined to recommend against than to recommend for. ... Why are we so reluctant to make value judgments about things not to do to patients? Is it because we are so fearful of potential litigation? Is it that we have become so financially conflicted? Or is it that we fear being accused of caring about cost? Maybe clinicians need the Task Force to make the call for us. And, for PSA testing, they did. If I was pressed to get off the fence, it's the call I would have made.

I couldn't agree more. Shared decision-making in PSA screening is an attractive concept that in practice leads to more harm than good. The Task Force was right to recommend that it stop, and that we instead advise patients not to get the test.