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but the risk of dying of prostate cancer is 2.9 percent. These data indicate that prostate cancer often grows so slowly that most men die of other causes before the tumor becomes a problem. At the same time, among men found to have prostate cancer, when it is confined to the prostate and treated, survival free of the cancer at five years is 100 percent, while for those in whom the cancer has spread at time of diagnosis, with distant metastasis, five-year survival is about 32 percent. Thus, tumors that have spread are generally not curable. Data on prostate cancer incidence: Ahmedin Jemal et al., “Cancer Statistics, 2009,” Cancer 59 (2009), pp. 225–249; Matthew R. Smith, “Effective treatment for early-stage prostate cancer—possible, necessary, or both?” NEJM (editorial) 364 (2011), pp. 1770–1772.

88 There is considerable debate about the use of PSA testing to screen for prostate cancer, reviewed in Michael J. Barry, “Screening for prostate cancer: The controversy that refuses to die,” NEJM 360 (2009), pp. 1351–1354. The difficulty is in distinguishing between finding those aggressive cancers that, with treatment, will save men’s lives and finding cancers that might never cause harm but are nonetheless treated, resulting in side effects of incontinence and impotence. Even after two recent large, randomized controlled trials, one conducted in Europe, the other in the United States, the issue of PSA testing is not settled.

The first of these recent trials is the European Randomized Study of Screening for Prostate Cancer, or ERSPC. The ERSPC evaluated 182,160 men between the ages of fifty and seventy-four who were randomly assigned to regular PSA screening, on average once every four years, or a control group that was not offered regular screening. The study used different recruiting and randomization procedures across seven centers in Europe. Furthermore, PSA cutoffs at which to perform a biopsy were not uniform but ranged between 2.5 and 4, with most centers using a cutoff at 3. There was incomplete information on how often the men in the control group at all centers had PSA screening done, although at one site in Rotterdam, the Netherlands, about a quarter of men in the control group had PSA testing. After nine years of follow-up, among men between the ages of fifty-five and sixty-nine, death from prostate cancer was 20 percent lower in the group that had regular screening. But again, we need to harken back to Susan Powell and look beyond the relative risk reduction of 20 percent to the “number needed to treat,” or here, the number needed to be screened. This turned out to be 1,410 men needed to be screened to prevent 1 prostate cancer death over nine years. The number is so large because most men screened did not have prostate cancer. Of those who did have a cancer detected by PSA screening, 48 additional patients would need to be diagnosed with prostate cancer to prevent a single prostate cancer death—that is, despite the detection of cancer, there was a modest impact on saving lives (1 saved life, 48 lives not saved). The study did not address quality of life, so there was no information about the side effects of impotence or incontinence from radiation or surgery or from the psychological burden of knowing that you have a cancer and not treating it actively (“watchful waiting”).

Critics of this European study pointed out that a substantial proportion of the control group received PSA testing, that about 25 percent of the cancers detected in the screening group did not receive curative treatment with either surgery or radiation, and since prostate cancer can grow very slowly, a follow-up of nine years to assess survival benefit may be too short; see Fritz H. Schroder et al., “Screening and prostate-cancer mortality in a randomized European study,” NEJM 360 (2009), pp. 1320–1328. The same issue of the New England Journal of Medicine carried the report from the Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial in the United States that found no benefit from annual PSA testing.

The PLCO study enrolled