Despite U.S. guidelines recommending against prostate cancer screening in elderly men, many specialists and older physicians still do these tests, a recent study suggests.

In 2008, the U.S. Preventive Services Task Force (USPSTF), a government-backed panel of independent physicians, recommended against routine prostate cancer tests for men at least 75 years old or with a limited life expectancy. They cited concerns that widespread screening often caught harmless tumors that didn't need treatment and led to unnecessary procedures with side effects like impotence and incontinence.

By 2011, the year the task force expanded its recommendation against routine screening to cover men of all ages, doctors in the Veterans Affairs health care system were already testing fewer elderly men than they did under the pre-2008 guidelines, according to the current study's authors.

But some types of doctors cut back on screening more than others as the guidelines shifted, the researchers found.

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Among the men with limited life expectancy still being tested in 2011, urologists screened 82 percent of them and doctors who were themselves over age 55 evaluated 41 percent of them. Geriatricians tested just 22 percent of these men.

"The training a type of provider receives may influence whether older men get PSA screening," said lead study author Dr. Victoria Tang, a researcher at the San Francisco Veterans Affairs Medical Center and the University of California, San Francisco.

Geriatricians and other providers whose training emphasizes evaluating the risks and benefits of screening in the contexts of life expectancy may be less likely to do unnecessary prostate cancer tests, Tang added by email.

To assess how characteristics of doctors influence which patients get screening, Tang and colleagues focused on a test for a substance in the blood called prostate-specific antigen (PSA). The PSA test can pick up early signs of cancer, but it can't reliably distinguish between fast-growing malignancies that need treatment and tumors that are growing too slowly to require treatment.

Researchers examined data on more than 826,000 veterans aged 65 years and older who had lab tests at the VA in 2011. This group included almost 204,000 men with limited life expectancy, meaning they had medical issues that made them likely to die within the next decade.

Overall, 56 percent of the veterans got PSA tests, including 39 percent of the men with limited life expectancy, Tang's team reports in JAMA Internal Medicine.

Screening rates ranged from 27 percent with physician trainees - who are typically younger and recently out of medical school - to 42 percent with staff doctors. Physicians aged 35 and under tested 29 percent of men.

Female physicians over age 55 did fewer tests than older male doctors, with screening rates of 38 percent and 43 percent, respectively.

These screening rates don't include men with a history of prostate cancer or symptoms of the disease such as unexplained weight loss or back pain or difficulty urinating. Recommendations against routine screening don't apply to these patients because testing them is medically necessary.

One limitation of the study is that VA patients may be sicker than the general population, the authors note. It's also likely that data from 2011 doesn't reflect changes in screening guidelines that came out late that year.

"The concept of more thoughtful screening is gaining wide clinical adoption amongst all specialists," said Dr. Alexander Kutikov, a urologic oncology specialist at Fox Chase Cancer Center in Philadelphia who wasn't involved in the study.

"Potential downsides of screening are now better appreciated and accepted by both general practitioners and urologists alike, so I have little doubt that more contemporary data would look different," Kutikov added by email.

Disagreement among doctors about who should and shouldn't get the PSA test still contributes to a variation in practice patterns, said Dr. Quoc-Dien Trinh, a urologist at Brigham and Women's Hospital and Harvard Medical School in Boston who wasn't involved in the study.

But this shouldn't happen with elderly men, Trinh added by email.

"What is clear is that men with limited life expectancy do not benefit from PSA screening," Trinh said. "They are much more likely to die with prostate cancer rather than from prostate cancer."