In a move that could lead to significant changes in medical care for older men, a national task force Monday recommended that doctors stop screening men 75 and older for prostate cancer because the search for the disease in this group is causing more harm than good.

The new guidelines, issued by the U.S. Preventive Services Task Force, represent an abrupt policy change by an influential panel that had withheld any advice regarding screening for prostate cancer, citing a lack of reliable evidence. Though the task force still has not taken a stand on the value of screening in younger men, the shift is certain to reignite the debate about the appropriateness of prostate cancer screening at any age.

Screening for prostate cancer is typically performed with a blood test measuring prostate-specific antigen, or PSA, levels. Widespread PSA testing has led to high rates of prostate cancer detection. Last year, more than 218,000 men were diagnosed with the disease.

Yet various studies suggest the disease is "overdiagnosed" — that is, detected at a point when the disease likely would not affect life expectancy — in 29 percent to 44 percent of cases. Prostate cancer often progresses very slowly, and a large number of these cancers discovered through screening likely will never cause symptoms during the patient's lifetime, particularly if that patient is older. Aggressive treatment of prostate cancer can greatly reduce a patient's quality of life, resulting in such complications as impotency and incontinence.

Past task force guidelines noted there is no benefit to prostate cancer screening in men with fewer than 10 years left to live. Since it can be difficult to assess life expectancy, it was an informal recommendation that had limited impact on screening practices. The new guidelines state that the age of 75 is the point at which screening is no longer appropriate.

The task force was created by Congress to analyze current medical research and to make recommendations about preventive care for healthy people.

"When you look at screening, you have a chance the screening will help you live longer or better, and you have the chance that screening detection and treatment will harm you," said Dr. Ned Calonge, chair of the task force and chief medical officer for the Colorado Department of Public Health and Environment. "At age 75, the chances are great that you'll have negative impacts from the screening."