Fewer men are being screened for prostate cancer, and fewer early-stage cases are being detected, according to two studies published Tuesday in The Journal of the American Medical Association.
The number of cases has dropped not because the disease is becoming less common but because there is less effort to find it, the researchers said.
The declines in both screening and incidence “could have significant public health implications,” the authors of one of the studies wrote, but they added that it was too soon to tell whether the changes would affect death rates from the disease.
About 220,800 new cases of prostate cancer are expected in 2015, along with 27,540 deaths, according to the American Cancer Society.
Screening for prostate cancer — like mammography for breast cancer — has long been the subject of intense debate, with advocates insisting that it saves lives, and detractors arguing that it leads to too much unnecessary treatment.
The decrease in testing is almost certainly the result of a recommendation against screening made in 2012 by the United States Preventive Services Task Force. The task force, an independent panel of experts picked by the government, found that risks outweighed the benefits of routine blood tests for prostate-specific antigen, or P.S.A., a protein associated with prostate cancer.
Because prostate cancer often grows slowly, the panel said, screening finds many tumors that might never have harmed the patient. But they are treated anyway. As a result, it concluded, testing saves few lives and leads too many men into unneeded surgery or radiation, which often leaves them impotent and incontinent.
An editorial accompanying the articles, by Dr. David F. Penson, the chairman of urologic surgery at Vanderbilt University Medical Center, acknowledged that too much screening can do harm but suggested that the pendulum has swung too far the other way.
Rather than issuing a blanket recommendation against screening, Dr. Penson said, it would be better to “screen smarter” by testing most men less often and focusing more on those at high risk.
One of the new studies, by researchers from the American Cancer Society, found that early-stage diagnoses of prostate cancer per 100,000 men age 50 and older dropped to 416.2 in 2012, from 540.8 cases in 2008, with the biggest decrease occurring between 2011 and 2012 — after a draft of the task force guidelines was released in October 2011. The authors estimated that the total number of diagnoses decreased to 180,043 in 2012 from 213,562 in 2011 — a difference of 33,519 cases.
That difference may indicate that many men were spared needless treatment — exactly what the task force had hoped to accomplish with its guidelines. But, the authors also say, “less screening or discontinuing screening may lead to missed opportunities for detecting biologically important lesions at an early stage and preventing deaths from prostate cancer.”
The percentage of men 50 and older who reported P.S.A. screening in the previous 12 months dropped to 30.8 percent in 2013, from 37.8 percent in 2010.
Although the study could not prove that the drop in screening caused the drop in diagnoses, the authors said it was the most plausible explanation.
The findings were based on data from cancer registries and national surveys that asked men about prostate screening.
A second study, by researchers from several medical centers, also found a significant decline in P.S.A. testing after the 2012 task force recommendations.
“With P.S.A. testing, we often detect cancers that don’t need to be treated — clinically indolent, meaningless cancers,” Dr. Penson said in an interview. “It is true that more men die with prostate cancer than of it.”
He said the recognition that many prostate cancers were indolent, or slow-growing, and not deadly had led to major changes in medical practice, making doctors less inclined to automatically operate if cancer is found.
The cancer society recommends that men discuss screening with their doctors to decide whether they should have it.
Some men, told the pros and cons, decide against having any screening, Dr. Penson said. Others opt for the testing, and if cancer is found, want it removed even though it might not be deadly.
But some who choose to be tested prefer another approach if cancer is found: “active surveillance,” which may involve repeated P.S.A. tests and a biopsy every other year to find out if the cancer is growing and becoming more aggressive.
“When you explain it, of course men look and say, ‘That would be great if I can avoid having surgery or radiation. If you think this cancer is not a problem, Doc, I’ll take that every day and Sunday,’ ” Dr. Penson said. “It’s not hard to convince patients.”
Dr. Penson said there had been two extremes in testing, neither satisfactory. First, doctors screened all men over 50 with P.S.A. tests and operated on all cancers. But now they may be heading toward the other extreme of not screening anybody.
Dr. Penson said better ways to screen were needed, methods that would let doctors zero in on the cancers that needed to be treated and could be cured. Promising new imaging techniques and blood tests for biomarkers that would reveal cancer are in the works, he said.
“But they’re not ready for prime time, so we’re stuck with the hand we’ve been dealt, the P.S.A. test, which is an imperfect test,” he added. “But we can do a better job with it.”