For decades, the American Cancer Society has been a stalwart advocate of steps to reduce cancer risk, including early testing. In a fine story in today's New York Times (registration required), Gina Kolata reports that they are about to back off on those guidelines, for breast and prostate cancers.
The essential issue is that early screening can find small tumors that might never become a problem, or might even disappear on their own. For these tumors, biopsies, further tests, or treatments are an unnecessary financial burden and also a health risk. On the other hand, many rapidly growing tumors may become serious problems in the time between tests.
In a related article (subscription required) published tomorrow [sic] in the Journal of the American Medical Association, entitled "Rethinking Screening for Breast Cancer and Prostate Cancer," three doctors review the disappointing results of twenty years of early detection, and conclude:
"One possible explanation is that screening may be increasing the burden of low-risk cancers without significantly reducing the burden of more aggressively growing cancers and therefore not resulting in the anticipated reduction in cancer mortality."
These results underline the need for measuring the comparative effectiveness of all medical procedures. Not everything that seems like a good idea really is. For every patient whose aggressive early cancer is stopped in its tracks (and whose doctors will vividly remember the events), there are others for whom the trauma, health risk, and expense were unnecessary--and avoidable.
In his book, The Healing of America (which I reviewed here), T.R. Reid notes that the PSA (prostate-specific antigen) test that is routinely given to older men in the U.S. is not paid for by the Public Health Service in the U.K. (p. 120). No doubt this is partially a matter of cost effectiveness. But as his British doctor explained, it is also a matter of medical effectiveness. It may seem brutal to trade off the few lives saved by early testing with lives lost by unnecessary intervention, but such statistical comparisons are, for now, our only option.
Ultimately, though, we need better tests: tests that can identify the molecular or other markers that distinguish between aggressive tumors that people will die from and more passive cancers that people will die with. As the JAMA authors conclude, "To reduce morbidity and mortality from prostate cancer
and breast cancer, new approaches for screening, early detection,
and prevention for both diseases should be considered."
[Update: Paul Raeburn at the Knight Science Journalism Tracker notes that although other outlets covered this issue, Kolata is unique in projecting a revision from the American Chemical Society.]
[Update (11/7/09): Science-Based Medicine has a fantastic, detailed discussion of the science behind this issue. Short message: keep screening.]