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Should we use the PSA test to screen for prostate cancer?

By Halley S. Faust, MD, MPH, MA and Paul T. Menzel, PhD

The U.S. Preventive Services Task Force (USPSTF) recommends against prostate-specific antigen (PSA)-based screening for prostate cancer (a grade D recommendation).

This recommendation applies to men in the U.S. population that do not have symptoms that are highly suspicious for prostate cancer, regardless of age, race, or family history. The Task Force did not evaluate the use of the PSA test as part of a diagnostic strategy in men with symptoms that are highly suspicious for prostate cancer. This recommendation also does not consider the use of the PSA test for surveillance after diagnosis and/or treatment of prostate cancer.

The American Urological Association (AUA) applauds the U.S. Preventive Services Task Force for its interest in reviewing the use of the prostate-specific antigen (PSA) test. However, we are concerned that the Task Force’s recommendations will ultimately do more harm than good to the many men at risk for prostate cancer both here in the United States and around the world.

Ought there be a higher threshold of evidence for prevention recommendations than for treatment recommendations? Two prior members of the US Preventive Services Task Force (USPSTF), Robert Wallace, MD and Diana Petitti, MD, independently make this argument in the recently published Prevention vs. Treatment: What’s the Right Balance? Most recently Petitti was co-chair when the task force released its 2009 mammography recommendation. In one of the book’s chapters she relates her experience in the difficult political process following this release.

Two weeks ago the USPSTF released another politically controversial draft recommendation, this time about PSA screening. Already in 2008 the task force recommended against screening, stating:

In men younger than age 75 years, the USPSTF found inadequate evidence to determine whether treatment for prostate cancer detected by screening improves health outcomes compared with treatment after clinical detection.
In men age 75 years or older, the USPSTF found adequate evidence that the incremental benefits of treatment for prostate cancer detected by screening are small to none.

The American Cancer Society concluded the same thing last year, and changed their recommendation accordingly. The USPSTF’s 2008 recommendation for men younger than 75 was one of uncertainty about benefits and harms. Now its recommendation is stronger: there is sufficient evidence to conclude more definitively against PSA screening.

We’ll leave the details of the reasons for the USPSTF’s change from 2008 to the 2011 draft recommendation to others to fight over. Instead we’d like to point out some obvious and not-so-obvious points about other dimensions of this controversy:

1. Advocates for specific diseases tend to use anecdote to support stringent recommendations.

So, for example, they will say, “I/my brother/my husband/my father would have died if he hadn’t had a PSA test at age 53.” Such a claim may be true, and we shouldn’t discount the sympathy involved in understanding it as a personal point of view. It does not, however, provide a sound basis for policy recommendations. For one thing, the person’s claim that an individual’s life was saved may not be true even though the discovery of the cancer that was assisted by the PSA test was experienced as lifesaving; for a variety of reasons, the person may not have died even had the test not been done. But even if the claim is true and this particular person’s life was saved, that alone is not sufficient to justify comprehensive screening.

Were we to use this “individual-saved” basis we could argue that every male should be screened for prostate cancer every week starting at age, for example, 30, for there have been known cases of prostate cancer in even younger men, and frequent screening would in theory pick up cancers even earlier. Yet we don’t screen so early or often because we say it isn’t efficient, and the risks outweigh the benefits (in this case risks include excess biopsies, false positive diagnoses with biopsies resulting in chemotherapy and/or radiation therapy, erectile dysfunction or impotence, urinary incontinence, infection, etc.).

2. There is a misperception that if we diagnose many types of asymptomatic cancers through screening we necessarily save lives.

This isn’t always true. If our treatment modalities are not very effective, or if postponed treatment does not affect longevity, then no lives are saved. And some lives may be severely inconvenienced by treatment without any long-term impact. We need to know that there is a causal link between screening populations and saving lives (or reducing disease-caused harm). Long-term longitudinal randomized controlled trials for prostate cancer screening have produced mixed results, as described in the USPSTF’s supporting documentation. And the members of the USPSTF have concluded that those studies, when taken as a whole, provide convincing evidence that mortality and morbidity are not substantially impacted.

3. We are all biased in how we look at information.

Mammographers who find breast cancers have the sense of a greater incidence of breast cancer in the under age 50 population than actually exists. Urologists to whom men are referred with high PSA results are biased toward thinking they can cure or save many of these men, without realizing what the results would be if they had done nothing, or if they hadn’t seen these men in the first place.

These cognitive biases skew our ability to make rational policy. As we point out in chapter 7 of Prevention vs. Treatment: What’s the Right Balance? our psychology is skewed by temporal and spatial proximity, often causing us to make prior hoc decisions later justified by post hoc rationalizations. The USPSTF is composed of individuals who don’t have these biases as much, and who don’t have financial interests in treating these diseases. Though for years members of other panels (e.g. radiologists doing mammography) recommending screening have argued their financial interests can be divorced from policy decision-making, studies have shown that financial (and other) self-interest and commitments substantially influence policy recommendations.

4. Underlying all of these points are values – sometimes explicitly stated and sometimes implicitly assumed.

Advocates for early and frequent screening are showing a value preference toward eschewing financial implications and sometimes treatment harms. They assume that early intervention essentially has only positive impacts on disease, or at least that almost any intervention is better than doing nothing. Even though it might look like advocates are putting a priority on prevention when they advocate for very frequent screening, when it comes to screening for asymptomatic disease they are actually implicitly stating that treatment cures are more effective than treatment harms, even if they have not been proven to be so. They are saying that it doesn’t matter how effective our prevention activities are in the long-term, because frequent attempts at detection, given faith in early treatment, is always better than doing nothing.

Sometimes doing nothing is more effective, like in most prostate cancer scenarios where (particularly elderly) men rarely die from slow-growing prostate cancers, usually succumbing to other maladies long before the prostate cancer develops into a life-threatening (or even morbidity-threatening) event. In younger men, on the other hand, the variety of cancer discovered is often too advanced or aggressive to be effectively treated. Furthermore, for younger and older men, follow-up treatments harm a considerable number of those who do undergo them. In this case, real prevention consists of doing nothing, for doing something (screening) starts a cascade of events that on average does more harm than good for the population as a whole.

5. Finally, we need to accept and admit that values for dealing with populations are somewhat different, or at least have a different emphasis, than values dealing with individuals.

For individuals we usually prioritize autonomy and privacy, which incorporates individual values and permits individuals to make decisions without necessarily having to justify them. This presumption of deference to individual choice and demand is reinforced by the larger funding function of membership in an insurance plan that permits financing of the individual’s decision.

Decisions for prevention can be individual, too – as is assumed by the task force for decisions about the PSA test – it recommends the decision be left to the discussion between the patient and doctor. But more so than in the case of treatments, recommendations on preventive measures are population focused. This is especially so in recommendations for or against routine screening. In turn, with prevention’s natural population focus, the need for resource trade-offs is more easily embraced. Decisions must take into account the commons, not just the desire of the individual.

All of these issues together do not have to imply that prevention should take a back seat to treatment. Just as patients and providers typically see the consequences of decisions about treatment vividly, so also farsighted individuals can identify strongly with the one person in thousands – perhaps themselves! – who will benefit from routine mammography or PSA testing. Generally, however, people do not see the stakes of prevention in such strong, individual terms. The fact that with certain types of cancers apparently sometimes they do – witness the reaction to the mammography and PSA testing reports – is both beneficial and dangerous. Beneficial because it can provide prevention with the same sense of psychological urgency that has provided treatments with such great leverage in modern health care systems, but dangerous because it can blind people to the risks, harms, and expense of preventive services.

Halley S. Faust, MD, MPH, MA is a preventive medicine physician and philosopher, and the President-Elect of the American College of Preventive Medicine. He is Clinical Associate Professor of Family and Community Medicine at the University of New Mexico. Paul T. Menzel, PhD has taught philosophy at Pacific Lutheran University (Tacoma, WA) since 1971. He has authored two books on moral questions about health economics and numerous papers on rights to health care and the role of values in shaping choices of health system structure. The authors are co-editors of Prevention vs. Treatment: What’s the Right Balance?

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One Response to “Should we use the PSA test to screen for prostate cancer?”
  1. [...] Menzel and I have written about a number of factors which should be involved in recommendations and/or resource allocation [...]

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