Cancer epidemiology 101

Originally posted on Common Sense Family Doctor on December 12, 2012.

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I've had many Twitter conversations with prostate cancer screening advocates who fear that the U.S. Preventive Services Task Force's "D" (don't do it) recommendation against PSA-based screening for prostate cancer will lead to a dramatic spike in prostate cancer deaths as primary care physicians screen more selectively, or perhaps stop screening at all. I seriously doubt these apocalyptic forecasts (for one thing, prostate cancer causes only 3% of deaths in men, and the decline in the U.S. prostate cancer mortality rate since 1990 hasn't had any appreciable effect on overall life expectancy). However, I recognize that reasonable people disagree with my review and the USPSTF's interpretation of the evidence. The American Cancer Society, for example, continues to support screening if men are adequately informed of the known risks and uncertain benefits. But it's one thing to argue from evidence, and quite another to argue from ignorance. Many of the tweets I've seen from urologists, unfortunately, represent the latter.