Fewer U.S. men are being screened for prostate cancer, and fewer cases of the disease are being diagnosed nationwide, according to two studies published Tuesday.
The big question, researchers said, is whether that trend is bad news or a step in the right direction.
At issue is the prostate-specific antigen, or PSA, test. For years in the United States, men age 50 and older routinely underwent PSA screening to help detect early prostate cancer.
But in 2012, the U.S. Preventive Services Task Force (USPSTF) -- a panel that advises the federal government -- came out against routine PSA screening.
The panel cited evidence that screening might do more harm than good: Prostate cancer is often slow-growing, and may never advance to the point where it threatens a man's life. So men diagnosed with early prostate tumors might needlessly be subjected to surgery, radiation and other treatments that can cause lingering side effects such as impotence and incontinence, the researchers said.
The two new studies, published Nov. 17 in the Journal of the American Medical Association, suggest that the USPSTF recommendations have had an impact.
In one study, researchers with the American Cancer Society (ACS) found that in 2013, 31 percent of U.S. men age 50 and older said they'd had a PSA test in the past year. That was down from 38 percent in 2010, and about 41 percent in 2008 -- the year the USPSTF began advising against routine PSA testing for men ages 75 and up.
At the same time, diagnoses of prostate cancer declined nationwide -- from more than 213,000 men in 2011, to about 180,000 in 2012.
The second study, by researchers from Brigham and Women's Hospital and Dana-Farber Cancer Institute in Boston, and Henry Ford Health System in Detroit, looked only at screening rates and found a similar pattern. The largest decline in PSA screening was among men ages 60 to 64: In 2010, 45 percent underwent screening, versus 35 percent in 2013. Men ages 50 to 54 also saw a big decline, with just 18 percent getting a PSA test in 2013 compared to 23 percent in 2010.
"The decline in incidence and the decline in the proportion of men getting screened likely means that doctors and patients are beginning to understand that it's not known whether prostate cancer screening saves lives," said Dr. Otis Brawley, the chief medical officer for the ACS.
On the other hand, Brawley said, it's clear that PSA screening can do harm.
"One of the things we do know," he said, "is that screening is more likely to diagnose the kind of [prostate] cancer that is not a threat to health and does not need treatment."
There have been 11 clinical trials testing the effects of PSA screening, Brawley said, and only two have found benefits for men's lives. "But all 11 show harms associated with screening," he added.
Others, however, were more worried about the trends in the ACS report.
"This study raises a troubling suggestion that we may be missing patients we want to find with screening," said Dr. Richard Greenberg, chief of urologic oncology at Fox Chase Cancer Center, in Philadelphia.
"Specifically, younger men who are currently not getting screened may have cancer 10 years from now that is no longer curable," Greenberg said.
Dr. David Penson, a urologic surgeon at Vanderbilt University, in Nashville, Tenn., also expressed concerns.
"We don't know how this will all play out," said Penson, who wrote an editorial published with the studies. "But I'd be willing to bet that this will be followed by an increase in prostate cancer mortality."
Penson agreed that in years past, PSA screening was probably overused. But the pendulum may be swinging too far in the other direction, he said.
"I would argue that we need to land somewhere in between," he said.
What's needed, according to Penson, is more research to better define which men are higher-risk and could benefit from more-intensive PSA screening. He pointed to one study from Sweden that found that a man's PSA level in his late 40s might help predict his risk of developing prostate cancer later in life.
That raises the possibility that a single PSA measurement at a relatively young age could help doctors figure out when and how often to do further testing, according to Penson.
Another way to address the issue is to further reduce "overtreatment" of prostate cancer. Men diagnosed with small, nonaggressive tumors do not have to be treated right away, Penson pointed out.
"They can opt for active surveillance," he said. "More and more men with low-risk prostate cancer are doing that."
Active surveillance means that a man's cancer is monitored over time, using PSA tests and possibly biopsies of the tumor.
For now, all three experts suggested that men talk with their doctors about the benefits and risks of PSA screening.
"I do hope physicians are talking to their patients and letting the patient decide whether or not to be screened," Brawley said.
For most men that discussion should begin at age 50, according to the American Cancer Society.
But men at increased risk should talk to their doctors starting at age 45, Brawley said. That includes black men and those with a brother or father who developed prostate cancer before the age of 65, according to the American Cancer Society.