There is no question that treatment of a prostate cancer is required for tumors that are aggressive and have advanced outside the confines of the prostate gland itself. But those that are locally confined have been the subject of great debate. A 2005 clinical trial showed that, for men under 65, treatment of the tumor prolongs survival. But for those older than 65, treatment provided no survival benefit. Nonetheless, only 10 percent of such older patients now undergo such a benign regimen, despite the fact that aggressive treatment can produce incontinence, impotence and other adverse effects. A large clinical trial to explore this discrepancy is now ongoing, but researchers from the Cancer Institute of New Jersey decided to see what data were available from other sources. Epidemiologist Grace Lu-Yao and her colleagues studied data on 14,516 men with prostate cancer, ages 66 and older, collected by the government's Surveillance, Epidemiology and End Results registry, which uses data from Medicare. None of the men received treatment in the first six months after diagnosis. The team reported Tuesday in the Journal of the American Medical Association that for men with locally confined prostate cancer, the risk of dying in the 10 years following diagnosis has fallen by more than 60 percent since the 1990s. Men with so-called intermediate-risk cancer diagnosed after 1990 have had a 2 percent to 6 percent risk of dying during the 10-year period, compared with a 15 percent to 23 percent risk before 1990. Only 4 percent to 11 percent of the men required chemotherapy, radiation or surgery to alleviate symptoms during the follow-up period. A 94 percent chance of survival without immediate treatment leaves little room for improvement by early treatme! nt, the authors said. Moreover, 56 percent to 60 percent of the men died during the follow-up period from causes not related to their prostate. There are several possible explanations for the finding. One important one is the introduction of the prostate-specific antigen, or PSA, test in the early 1990s, a blood test that can show the presence of tumors. The PSA test typically produces a tumor diagnosis six to 13 years earlier than a diagnosis based on clinical symptoms, and that alone could account for the increase in survival. But the PSA test also leads to a large number of false positive tests that require invasive and expensive procedures to confirm the findings. As a consequence, most major cancer groups do not call for routine screening of men with the test, leaving it to a discussion between the physician and patient. 