Prostate cancer & Blacks: The screening conundrum

Eight out of a 100 men receiving the prostate-specific antigen (PSA) screening test for prostate cancer will have an abnormal result. However, only three of those eight will have prostate cancer. The other five are falsely positive for the disease. They endure the psychological stress of getting an abnormal PSA result, and then the discomfort of a prostate biopsy.

In the March 23, 2009 issue of the New England Journal of Medicine, the first reports from two large, multicenter, randomized controlled trials on the effectiveness of PSA screening appeared. In the United States, the Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial by Andriole et al reported no mortality benefit from combined digital rectal examination (DRE) and PSA tests during a median follow-up of 11 years. However, the European Randomized Study of Screening for Prostate Cancer (ERSPC) trial of Schroder et al found an absolute reduction of 7 prostate cancer deaths per 10,000 men screened.

As noted by Dr. Michael Barry in an accompanying editorial in the same issue of the New England Journal of Medicine, the PLCO trial is much smaller than the ERSPC, and, as a result, its estimates of the effects of prostate cancer screening are not as accurate as the European study. On the other hand, the ERSPC has not, as yet, assessed the trade-offs for the very modest effect of the PSA screening. More than 14,000 men would have to be screened and 48 treated in order to prevent 1 prostate cancer death — if we assume the ERSPC’s estimate of the screening’s effect is correct. In the ERSPC trial, 73,000 men were in the screening group, more than 17,000 biopsies were performed, 2-3 times as many men in the screened group were diagnosed with prostate cancer, 2-3 times as many were treated with radical prostectomies, and 2-3 times as many received radiation therapy. As Dr. Barry commented in his editorial, “Although the PLCO trial may not have had enough power yet to detect the same modest benefit of screening as seen in the ERSPC trial, it clearly has adequate power to show the important harm of overdiagnosis and overtreatment.”

However, some would argue that the situation is different for African-American men. The burden of this disease does not fall evenly across the population. African Americans get it more often. African Americans get it at a younger age. African Americans die from the disease in disproportionately high numbers. The problem for African-American men, this argument goes, is not overdiagnosis and overtreatment of prostate cancer, but rather its underdiagnosis and undertreatment.

That’s a straw-dog argument. It really highlights the fact that African Americans have poor access to health care; however, it doesn’t assess the effect of screening on African-American men. If you look at the United States, out of 100 men, 20 will develop prostate cancer in their lifetime. Of that 20, three will die from their prostate cancer. Among African-American men, five of 20 will die from their prostate cancer. Although we can’t tell our patient with prostate cancer sitting in the exam room in front of us whether he will die from the disease, it’s clear that most men with prostate cancer won’t die from it. PSA testing, therefore, leads to finding and treating clinically insignificant cancers — for both whites and African Americans.

Clearly, the most prudent thing for clinicians to do is to help our patients make an informed medical choice. We should give them the facts regarding the very modest benefit of prostate cancer screening today versus the harm of overdiagnosis and overtreatment of this disease and let our patients make the choice to be screened or not.

Monday, May 18th, 2009 at 03:52