CHICAGO (Reuters) - New guidelines from the American Cancer Society urge doctors to make sure their patients fully understand the risks as well as the benefits of prostate cancer screening before any blood is drawn.

The updated guidelines issued on Wednesday reflect the ongoing debate over the prostate-specific antigen, or PSA, blood test after two large studies last year produced conflicting results about whether it actually saves lives.

“With these newly updated recommendations, the American Cancer Society places even stronger emphasis on shared decision-making between clinicians and patients,” Dr. Otis Brawley, chief medical officer of the American Cancer Society, said in a statement.

Prostate cancer is the second most common cancer in men worldwide after lung cancer, killing 254,000 men a year.

Doctors have routinely recommended PSA tests to men over 50 in the belief that early diagnosis and aggressive treatment for any cancer is better than standing by and doing nothing.

But a study published last August in the Journal of the National Cancer Institute found routine screening for prostate cancer resulted in more than 1 million U.S. men being diagnosed with tumors who might otherwise have suffered no ill effects from them.

Prostate cancer treatments, including surgery or radiation, can cause incontinence and erectile dysfunction in about a third of patients. Many men also experience bowel problems.

“These risks are not inconsequential. We do want to be sure that men know all of this before they make their decision of whether or not to be screened,” said Dr. Andrew Wolf of Virginia Health System, who chaired the advisory committee that developed the guidelines published in CA: A Cancer Journal for Clinicians.

AVERAGE RISKS

The updated guidelines recommend that men of average risk get information about the risks and benefits of screening by age 50 before making a decision about the test.

Men at higher risk -- including blacks and men with a father or brother who was diagnosed with prostate cancer -- should get this information by age 45.

Men with multiple family members who have been diagnosed with prostate cancer before age 65 should have the prostate cancer discussion with their doctors at age 40.

The group also recommends that doctors use patient decision aids, including one developed by the Foundation for Informed Medical Decision Makinghere, which can help men weigh the risks and benefits of screening.

“Hopefully, what we’re promoting is that doctors provide as balanced a presentation of the issues as they can,” Wolf said in a telephone interview.

And they say no screening should be done without giving men a chance to weigh their options.

“We are increasingly aware of the fact that many men who do choose to be screened are diagnosed with an early prostate cancer that leads to treatment, and if they had not been screened, they never would have known about a cancer that was never destined to harm them,” Wolf said.

“That is a very real risk of prostate cancer screening that has become increasingly clear since our last guideline update in 2001,” Wolf said.

“The other risks are those of treating prostate cancer that is found through early detection.”