Wednesday, May 23, 2012


The United States Preventive Services Task Force, having studied the potential risks and benefits of the prostate-specific antigen blood test, or “PSA,” has concluded that hazards attending the test outweigh potential benefits. The task force found that at best, one man in every thousand tested may avoid death as a result of the screening, while another man for every three thousand tested will die prematurely as a result of complications from prostate cancer treatment, and dozens more will be seriously harmed.

As you might expect, this finding hasn’t been met with universal hallelujahs. Some prostate cancer advocacy groups as well as the American Urological Association take issue with the published recommendation. In response, Dr. Michael LeFevre, the co-vice chairman of the task force and professor of family and community medicine at the University of Missouri, said, “Change is hard. It’s hard for all of us, both within and outside the medical profession, to accept that not all cancers need to be detected or treated, and that there are harms associated with screening, and not just benefits.”

The broader issue here is the nature of medicine itself. We popularly believe science to be a yes-or-no proposition. We put much stock in its pronouncements since it is, after all, an elegant method for gaining knowledge. But the answers the universe reveals respond only to the questions we ask, and what we ask is necessarily limited since as mere humans we can’t see the Whole Picture. We ask, “Does a heightened PSA level indicate cancer?”, and the response is, “It often does.” That is, it sometimes doesn’t. In addition, cancer doesn't necessarily elevate the PSA. Further testing and treatment can be tangibly harmful, possibly even more than prostate cancer itself.

Of coure, we love when medical science seems to produce a miracle. Take diethylstilbestrol, or DES, a hormone that prevented miscarriages in women between 1940 and 1971. This seemed a terrific advance until it was learned that the children of these women suffered huge rates of genital cancer. Who knew, in 1940, to ask about cancer in these women’s children?

Every few years the argument resurfaces about whether mammograms cause more breast cancer than they detect. Today the weight of evidence leans toward the more benign, yet experts nevertheless recommend ever more judicious use of mammograms.

And so it goes with a multitude of tests and treatments. I raise this issue as a reminder to take medical science with a dose of humility. That we docs are doing the best we can is both the good news and the bad news. Keep in mind the apocryphal story of the medical school dean who, addressing his graduating class, said, “I’m sorry, but about a third of what we’ve taught you is untrue…we just don’t know which third.”

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