The U.S. Preventive Services Task Force's recommendation against routine use of a blood test that can offer early detection of prostate cancer has led to puzzlement and anger. The reaction has been similar to that following the group's suggestion two years ago that routine mammograms be sharply curtailed. As with mammograms and breast cancer, many of those who received treatment for prostate cancer after a blood test showed elevated levels of prostate-specific antigen — a marker for prostate cancer — are convinced that the screening saved their lives. To them, eliminating the test is like saying they should have been allowed to die. That sort of argument is powerful but flawed, and it risks subjecting millions of other men to unnecessary and potentially dangerous consequences.

A recommendation like this one is bound to be interpreted in Washington and by some members of the public as an effort by the government to ration care to save money on health costs. But the cost of the test has nothing to do with the task force's recommendation. The issue is whether early detection of prostate cancer saves lives or whether the treatment is too often worse than the disease. Relying on large-scale clinical trials in the United States and Europe, the task force found little or no reduction in prostate cancer deaths as a result of screening, but much harm — even death — from efforts to treat prostate cancer based on elevated PSA levels and biopsies.

For a public that has long been conditioned to believe that early detection and treatment are the best ways to survive cancer, that's hard to grasp. But the truth is, not all cancers are created equal, and prostate cancer in particular may be ill suited to that approach. Autopsies show that prostate cancer is extremely common, particularly as men age, but it often presents no risk in and of itself. Some prostate cancers are aggressive, and there is no evidence that early detection through a test like the PSA makes any difference in survival rates. But the vast majority of men who have cancer cells in their prostates will suffer no ill effects from the disease. What you don't know, in most cases, won't hurt you.

But treatment of prostate cancer involves serious risks. According to the task force, 1 million men received surgery, radiation or both as a result of a PSA test from 1986 to 2005. According to an article in the Annals of Internal Medicine that provided an independent assessment of the task force's work, about 0.5 percent of those who received surgery after a PSA test died within 30 days. Surgery also increased risks for serious cardiovascular complications. Both surgery and radiation significantly increased risks for incontinence, impotence and other health problems.

That makes a case for why prostate cancer shouldn't always be treated aggressively — but not necessarily for discontinuing the screening. Johns Hopkins Hospital has long been on the forefront of research into the idea of "watchful waiting," that is, carefully monitoring the progression, if any, of a prostate cancer rather than treating it immediately with surgery or radiation. The Active Surveillance program there has reported good results, as have others like it.

That raises the question: If the problem is complications stemming from over-treatment, why not focus on that instead of on the test itself? Part of the answer lies in the fear of cancer; many patients find themselves unable to live with the idea of having a cancerous organ in their bodies, even if they are told the risk of harm is low. And part of the answer lies in the nature of the PSA test itself. Unlike a mammogram, getting a PSA test requires nothing more than for a doctor or nurse to check a box on the form that accompanies a blood sample to a lab. It is so easy and so routine that doctors and patients rarely discuss the merits of the test or what they would do with the results.

The task force's recommendation doesn't mean the PSA will go away. The federal government is already required, by law, to pay for it through the Medicare program no matter what the Preventive Services Task Force says. But it will certainly raise awareness among doctors and patients about the test's limitations and the risks of prostate cancer treatment. That alone has the potential to save thousands of lives.