Find prostate cancer early, save a life.

That message has been pervasive since 1986, when a blood test for prostate cancer first hit the market. But more evidence suggests that, in many or even most cases, the message is wrong.

The latest blow against prostate-specific antigen (PSA) testing came Friday from a large, long-term study that found routine testing in men ages 55 to 74 did not prevent deaths from prostate cancer.

“The message is that routine mass screening is not the way to go,” said one of the leaders of the study, Gerald L. Andriole Jr. of Barnes-Jewish Hospital in St. Louis. “But we don’t need to throw out PSA testing altogether.”

Andriole said the large majority of prostate cancers found by PSA testing were slow growing and nonlethal. But no test can sort out the potentially deadly cancers from the nonfatal kind, forcing many men to undergo unnecessary surgery, radiation and drug therapy. Those treatments often leave men incontinent and unable to function sexually.

The new study, however, is unlikely to settle the long-running debate over the value of PSA testing, as prominent advocates of the tests said the results did not change their views.

“It’s a flawed study,” said William J. Catalona, a prostate cancer surgeon at Northwestern University in Chicago who helped develop the PSA test. “It doesn’t really address the question of whether PSA screening saves lives.”

Launched in 1993, the National Cancer Institute-funded study followed 76,000 men at 10 sites nationwide for about 13 years. Half received annual PSA tests for six years and also received digital rectal exams, which can help detect some prostate tumors. The other half, in the “community care” group, continued under the care of their regular doctors. Although doctors found about 12 percent more cancers in the PSA screening group, both groups had about equal numbers of deaths. Detecting the extra cancers, in other words, did not reduce the death rate from the disease.

“There is a tendency to believe that if a test finds disease, that must be a good thing,” said Otis Webb Brawley, a cancer screening expert and chief medical officer of the American Cancer Society. But that isn’t necessarily so, he said, adding, “I’m very worried about ‘auditorium medicine,’ where a long line of guys waits to get screened and there is no discussion or education about the potential risks and benefits.”

Ideally, none of the men in the “community care” group would have received PSA testing. That would have made the study a clearer test of whether the screening saves lives. But in the 1990s, primary care physicians rapidly adopted routine screening in men 50 and older. About half of the men in the “community care” group did, in fact, receive PSA testing.

That factor muddied the results, said Jonathan W. Simons, an oncologist and chief executive of the Prostate Cancer Foundation, a patient advocacy group. “The study is so fundamentally flawed it doesn’t move us forward in what we need to do to reduce deaths from prostate cancer.”

The study, published in the Journal of the National Cancer Institute, was released as doctors, researchers and policymakers are increasingly questioning whether many tests, drugs and procedures are being overused and unnecessarily driving up health-care costs.

For years, doubts have been raised about the wisdom of widespread PSA testing. Many prostate surgeons and the American Urological Association have long argued that routine screening saves lives.

Politicians and celebrities have reinforced that message. In 2009, former U.S. senator Robert J. Dole appeared on CNN’s “Larry King Live” to encourage men to get tested, with a slew of other famous faces — Colin L. Powell, Norman Schwarzkopf Jr. and John McEnroe among them — backing him up.

But the NCI has never recommended routine screening. And the American Cancer Society counsels men older than 50 to discuss the test with their doctors.

In October, a national debate erupted after an influential government panel concluded that most men should not be routinely tested. Screening does not save lives, the U.S. Preventive Services Task Force found in its draft recommendation, but instead encourages unnecessary treatment.

That conclusion drew an immediate backlash that reverberated all the way to the presidential campaign. At an October debate, Republican candidate Newt Gin­grich said the task force recommendation “is basically going to kill people.” Gingrich cited one of his advisers, former NCI and Food and Drug Administration chief Andrew von Eschenbach, in the statement. (Eschenbach told The Washington Post that Gingrich had quoted him correctly.)

Still, the new results had some testing proponents softening their message. “Maybe we don’t need to do PSA [tests] every year,” said Andrew K. Lee, an oncologist at the M.D. Anderson Cancer Center in Houston. “Maybe we can initially do a few PSA [tests] as a baseline and then do them every couple years.”

Study leader Andriole said African American men, who are at higher risk of dying from the disease, and men with a family history of prostate cancer are most likely to benefit from regular screening.

Brawley said that men age 50 and up should talk with their doctors about the testing. “This is a lot more complicated than ‘just get the test,’ ” he said.

Simons said that while the benefits of regular PSA testing remain uncertain, one thing is clear: “We need a better test than PSA.”