The rate of prostate screenings and the incidence of prostate cancer diagnoses have both declined sharply since an expert panel issued controversial recommendations that men should no longer have the simple blood test that can reveal the disease, researchers reported Tuesday.

The U.S. Preventive Services Task Force concluded in 2012 that the prostate-specific antigen (PSA) test causes more harm than good, saving few lives but prompting unnecessary surgery, radiation and side effects among men who would never die from the often slow-growing cancer. Except for those with high risk for the disease, men should avoid the blood test, the panel said.

Four years earlier, it had issued similar guidelines for men older than 75. Together, the recommendations countered two decades of medical practice.

The result has been a clear decline in the number of men being tested and the discovery of cases of prostate cancer, researchers reported in the Journal of the American Medical Association.

Otis Brawley, chief medical officer for the American Cancer Society and an author of the new study, said the decline is a positive sign if it means that more doctors and patients are discussing the pros and cons of the screening and making decisions together.

“It’s only a good thing if [the numbers] went down because doctors and patients consciously decided together that it shouldn’t be done,” Brawley said.

“I think it’s terrible to tell a man he must get screened,” he added. “I think it’s terrible to tell a man he can’t get screened.”

The study found that 30.8 percent of men ages 50 or older reported getting the PSA test in 2013, down from 37.8 percent in 2010 and 40.6 percent in 2008. It also found that the rate of prostate cancer diagnoses in that age group fell from 534.9 per 100,000 in 2005 to 416.2 in 2012. About 33,519 fewer men received a diagnosis of prostate cancer in 2012 than in 2011, the researchers estimated.

A second study in the same journal found a similar drop in the proportion of men who had the PSA screening.

Numerous studies have shown that if PSA screening saves lives, the number is very small, Brawley said. At the same time, surgery and radiation for the disease often lead to side effects that affect quality of life. As many as 50 percent of men who have the most radical surgery or radiation experience impotence or urinary incontinence. Some have bowel problems.

“Screening is really good at finding cancer that doesn’t need to be cured,” he said. But for some men, hearing a diagnosis of cancer and doing nothing but monitoring it is too difficult, he said.

Major medical organizations remain split on guidelines, with some cancer and urology groups recommending a less absolute position on routine screening. Matt Tollefson, an associate professor of urology at the Mayo Clinic in Minnesota, said that he recommends “selective” PSA testing for men at high risk for the disease, including African Americans and men with a family history of the disease.

Tollefson said that in past years, the pendulum clearly had swung too far toward routine screenings, which resulted in overtreatment. Now the question is how far back it should go, he said. “Time will tell what happens to prostate cancer mortality,” as well as illness, he said.

In an editorial accompanying the studies, David F. Penson of Vanderbilt University’s department of urologic surgery said “there is reason to be concerned” about both the drop in screenings and the decline in cancer diagnoses.

“It is time to accept that prostate cancer screening is not an all or none proposition and to accelerate development of personalized screening strategies that are tailored to a man’s individual risk and preferences,” Penson said in the editorial.

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