More than 100,000 American men who each year undergo “curative” therapy for low-risk prostate cancer should consider delaying treatment until the disease gets worse, and possibly put it off forever, a committee of experts convened by the federal government said Wednesday.

The go-slow strategy is “a viable option” because there is no convincing evidence that surgery or radiation therapy increases survival, and there is good evidence that those procedures worsen quality of life, the panel concluded after a three-day meeting at the National Institutes of Health in Bethesda.

About 240,000 American men are diagnosed with prostate cancer each year, and in 130,000 the tumors are “localized and low-risk.” About 90 percent of the low-risk group now opt for curative treatment, but all are candidates for strategies based simply on following the patient closely, the panel said.

“Our panel found that men with localized and low-risk prostate cancer should be closely monitored, permitting their treatment to be delayed until warranted by disease progression,” Patricia A. Ganz, a physician at the University of California at Los Angeles who headed the 14-member committee, told reporters Wednesday.

She said she expected the conclusions to be both controversial and influential.

“An NIH-vetted document that describes this as a reasonable approach . . . can be very powerful,” she told reporters.

The committee’s carefully worded 19-page statement is the second blow this season to American medicine’s approach to the most common cancer in men. In October, a different panel that advises the government on disease prevention said most men should not be screened for prostate cancer with the PSA blood test because finding the disease early leads to no clear benefit.

The latest panel only considered what is known about management of tumors confined to the prostate gland that also appear relatively normal when viewed under a microscope. It did not discuss treatment of fast-growing, wildly abnormal cancers.

Its conclusions appeared to be generally, but not universally, supported by people who attended the conference, where researchers and practitioners Monday and Tuesday presented data about the “state of the science” of low-risk prostate cancer treatment .

“I think they did a wonderful job,” said Otis W. Brawley, chief medical officer of the American Cancer Society. “I’m hopeful this document will cause doctors and patients to consider ‘active surveillance’ as a legitimate treatment for this disease.”

Jerry Sims, a 72-year-old patient advocate who traveled from Pinckney, Mich., to attend the conference, called the panel’s work “a big step forward.” Eight years ago, he had a radical prostatectomy — treatment he thinks he embraced too quickly.

“In most places you can’t get married without waiting a few days. I don’t understand why there isn’t a cooling-off period for this disease,” he said.

However, Merel Grey Nissenberg, a San Diego malpractice lawyer who heads the California Prostate Cancer Coalition, said she was not entirely happy.

“I am worried that the pendulum will swing too far the other way and that patients will be convinced to opt for active surveillance when in fact they need curative treatment,” she said.

Prostate cancer is common and widely variable in behavior. By the time men are in their 80s, nearly three-quarters of them have it.

Diagnosis of the disease in American men rose steeply after a blood test for “prostate specific antigen” (PSA) was introduced in 1987. A protein produced by the prostate gland, PSA rises with age and when cancer is present.

With the advent of that testing, an American man’s chance of being diagnosed with prostate cancer in his lifetime rose from 8 percent to 17 percent. Most of the cancers found, however, were slow-growing and confined to the gland. Patients with cancers considered low- and intermediate risk (with a so-called “Gleason score” of 5, 6 or 7) had just under a 5 percent chance of dying of prostate cancer within 10 years of diagnosis.

Curative treatment consists of surgically removing or destroying the entire prostate gland, which wraps around the urethra, the tube that carries urine from the bladder to the penis. The prostate produces fluid that helps carry sperm during sexual intercourse.

“Both radical prostatectomy and radiation therapy patients experience worse urinary and sexual functioning in comparison to observation patients. These differences persist over time,” the panel wrote.

There are two “observational strategies” for low-risk prostate cancer.

With “active surveillance,” a patient gets periodic physical exams, prostate biopsies and PSA tests, and is offered surgery or radiation if the tumor begins to grow quickly. The few studies of this approach show that about half of patients undergo curative therapy within five years.

The second strategy is “watchful waiting,” in which treatment is given only when the disease causes symptoms, such as pain from a tumor that has spread to the bones, or urinary blockage. Watchful waiting is most common in elderly men, who have a high likelihood of dying of some other disease before their prostate cancer kills them.

Most patients don’t consider those strategies because physicians do not explain them adequately or often describe them as “doing nothing.” Shock at a cancer diagnosis also leads many patients to think they should pursue the most aggressive treatment possible. The panel, in fact, suggested that rebranding might be in order.

“Because of the very favorable prognosis of low-risk prostate cancer, strong consideration should be given to removing the anxiety-provoking term ‘cancer’ for this condition,” the panel wrote. It did not, however, suggest a new name.

The panel noted that much remains to be learned about optimal treatment of prostate cancer. But because there are “insignificant mortality differences” in treatment approaches for low-risk disease, much of future research should focus on finding out exactly how observational strategies affect quality of life and on finding ways to better explain options to patients, the panel wrote.