Wednesday, March 15, 2017

Is screening African American men for prostate cancer warranted?

Regular readers of my blog know that I believe that the harms of prostate-specific antigen (PSA) screening for prostate cancer outweigh the benefits, if benefits exist at all. That isn't to say that I will not order the test in a man who understands the risks and expresses a clear preference to be screened. In a recent editorial in American Family Physician, I explained my approach to counseling patients about potential screening harms:

Many older men, especially those who have received PSA tests in the past, may be surprised to learn that screening is no longer routine. Primary care physicians should anticipate this possibility and be prepared to explain that more is now known about the outcomes of testing. Phrases that may be helpful to communicate changes in our understanding of the evidence include “the PSA test is now optional,” “this test has limitations and may not be for everyone,” and “there are some important downsides to being tested.” These strategies, combined with decision aids, should help our patients make informed choices that are consistent with their personal preferences on PSA screening.

One question that arises frequently at the hospital and clinic where I precept family medicine residents is: what about African-American men? Should we advise that they be screened because they have a higher prostate cancer incidence and mortality than other racial or ethnic groups? This question came up during the development of the U.S. Preventive Services Task Force's 2008 recommendations, which included this statement:

Older men, African-American men, and men with a family history of prostate cancer are at increased risk for diagnosis of and death from prostate cancer. Unfortunately, the previously described gaps in the evidence regarding potential benefits of screening also apply to these men.

The publication of the U.S. and European randomized trials of PSA-based screening, which ultimately caused the USPSTF to change its "I" (insufficient evidence) statement to a "D" (recommend against) in 2012, unfortunately did not do much to clarify benefits and harms of screening in men of African descent, who comprised only 4% of participants in the U.S. trial and an unknown (but probably low) percentage of those in the European trial. And even the subsequent negative findings of the Prostate Cancer Intervention Versus Observation Trial (PIVOT), whose participants were more than 30% African-American, didn't discourage authors in academic journals and prominent medical blogs from arguing that Black men need separate prostate cancer screening guidelines.

What troubles me about this position is that race is as much a social construct as it is a biological one. Much of the disparity in prostate-cancer mortality between African-American and Caucasians can be explained by lower access to and quality of care, rather than a genetic predisposition for more aggressive and/or lethal cancers. In contrast to national data, studies of equal-access healthcare systems in the U.S. such as the Veterans Health Administration and the Department of Defense found no differences in prostate cancer mortality between Black and White men.

In this context, the USPSTF recently published a thoughtful methods paper explaining their approach to developing recommendations for diverse populations. The research plan for their updated systematic review on prostate cancer screening included explicit questions about whether the effectiveness or harms of PSA-based screening or treatment approaches varied by subpopulations, including race. Such data may or may not be sufficient to permit the Task Force to assign a separate recommendation letter grade to screening in African-American men this time around (I suspect it will not), but it will hopefully result in more helpful guidance for primary care clinicians.

Here is what I currently tell African-American men over 50 who are considering the PSA test: "In general, this test is more likely to harm than to help. Your personal risk of having prostate cancer is higher than other men, which may make it more likely that you benefit from testing, but also increases the potential harms. So while the general statistics on PSA screening might not apply to you specifically, the decision to be screened still comes down to your personal preference."

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