NEW YORK - Doctors should stop routine prostate cancer screening of men over age 75 because there is more evidence of harm than benefit, a federal task force advised on a hotly debated topic.

The U.S. Preventive Services Task Force, which made the recommendation Monday, reported finding evidence that the benefits of treatment based on routine screening of this age group "are small to none." However, treatment often causes "moderate-to-substantial harms," including erectile dysfunction and bladder control and bowel problems, the task force said.

The new guidance is the first update by the task force on prostate cancer screening since 2002. Its last report concluded there was insufficient evidence to recommend prostate screening for men of all ages.

In recent years, there has been a growing debate about the value of the somewhat imprecise PSA blood test to detect cancer, as well as the value of treating most prostate cancers. A positive result from the test must be confirmed by a biopsy. And even then, there is no foolproof method of identifying aggressive tumours from slow-growing ones. A number of experts contend patients are being overtreated.

"The issue of screening for prostate cancer is frankly an area of medicine that remains somewhat unsettled," said Dr. Durado Brooks, a prostate cancer specialist for the American Cancer Society. "While it's clear there is benefit to a significant number of men, it's equally clear that many men end up being diagnosed and treated for cancers that would likely not have caused them any significant harm."

Most major U.S. medical groups recommend doctors discuss the potential benefits and known harms of prostate screening with their patients and make individual decisions. And most agree such testing shouldn't occur before age 50.

The federal task force, which sets the nation's primary care standards, reviewed past research in reaching its conclusion and "could not find adequate proof that early detection leads to fewer men dying of the disease," task force chairman Dr. Ned Calonge of Denver said in a statement.

The cancer society's advice for screening differs from the task force's because it doesn't set a fixed age to stop screening, Brooks said. It suggests that men shouldn't be offered screening if they aren't expected to live another 10 years.

"That's because every 75-year-old is not created equal," said Brooks.

While some have health problems and aren't likely to live long, others are "very active, very vigorous and have minimal health issues, and many of those men are going to live into their late 80s or 90s," Brooks said.

Prostate cancer is the most common cancer in American men -- about 220,000 cases will be diagnosed this year. It is the second leading cause of cancer deaths in men. But most tumours grow so slowly they never threaten lives.

Earlier this year, a study found that older men who already had early-stage prostate cancer were not taking a big risk by not treating it right away. The vast majority were alive 10 years later without significantly worrying symptoms or had died of other causes.

Prostate cancer treatments are tough, especially on older men. Some doctors instead recommend "watchful waiting" to monitor signs of the disease and treat only if they worsen, but smaller studies give conflicting views of the safety of that approach.

The new guidelines from the Preventive Services Task Force were published in this month's Annals of Internal Medicine.