TUESDAY, Aug. 15 (HealthDay News) -- To treat or not to treat?

A new study finds that more than half the American men who got surgery or radiation treatment for their prostate cancer might have fared just as well with a "wait and see" program that didn't include active treatment.

Because tumor progression can vary widely among patients, "there is a great paradigm shift occurring in prostate cancer," said study co-researcher Dr. David C. Miller. "There are some cancers for which treatment will clearly be beneficial," he said. "In other cases, we can avoid aggressive treatment, with all its side effects."

Doctors now are trying to determine which men would be better off without treatment, he said.

His team published its findings in the Aug. 16 Journal of the National Cancer Institute.

"The motivation for the study was that we have learned more about how frequent side effects of treatment are, and what the best therapies are," explained Miller, who took part in the study while at the University of Michigan and is now a urological oncology fellow at the University of California, Los Angeles.

The study was done on "a big population level," looking at more than 64,000 men listed in a U.S. National Cancer Institute registry as having been diagnosed with early prostate cancer. They were divided into having either high-risk or low-risk cancers on the basis of factors affecting the aggressiveness of the cancer.

From 2000 to 2002, more than half of the 24,835 low-risk men had undergone radiation treatment or surgery in the first months after diagnosis, the researchers reported.

Age appeared to influence treatment options. Men under age 55 were most likely to be treated with surgery, instead of "watchful waiting," the researchers reported. Low-risk men over 70 were most likely to receive radiation treatment -- even though they often have slow-growing tumors and will die of something other than their cancer.

A large-scale study was needed because "there are tens of thousands of men for whom this decision is relevant," Miller said. The American Cancer Society estimates that 234,000 American men will be diagnosed with prostate cancer this year and 27,350 will die of it.

The trick, according to Miller, is to spot those men who require active treatment and those who can simply be followed over time.

Several studies are under way trying to identify those men who are unlikely to die of their prostate cancers no matter what the treatment, as well as those who are less likely to benefit from treatment, Miller said.

One such study is being conducted by a team at the University of Texas M. D. Anderson Cancer Center in Houston. It's testing the concept of "watchful waiting," whose definition has changed over the years, said Dr. Jeri Kim, an associate professor in the genitourinary medical oncology department.

"In the old days, we would follow a patient until symptoms developed," she said. "Now, we talk about actively following the patient with different tools."

Those tools include the patient's "Gleason score," a measure of how cancerous prostate cells appear under the microscope; the standard prostate-specific antigen (PSA) blood test score; ultrasound examinations and biopsy reports, Kim said.

The trial started in February. It will enroll 650 men with small, early prostate cancers for years, looking at what factors might make a tumor turn aggressive, Kim said. "There really isn't a national set of guidelines for patients to be watched," she said. "Were trying to define some and also come up with new markers to detect cancer growth."

Several medical factors such as the Gleason score now can influence the decision between treatment and watchful waiting, Miller said. But a man's attitude is also important, he said.

"Are the men comfortable with the idea that they are going to live with a cancer diagnosis?" he said. "Some men have strong feelings about being treated. Men who have watchful waiting must come in for follow-ups and be comfortable with the idea that they have a cancer that is being monitored."

The newly reported study "doesn't propose to have the right answer to the question, but to say how big the problem is," Miller said.

Another report in the same issue of the journal found that prostate cancer is more easily detectible in men taking finasteride, a drug prescribed for an enlarged prostate. Finasteride made a PSA test result more definitive, concluded the report by physicians at the University of Texas Health Science Center in San Antonio.

More information

There's more on about prostate cancer at the U.S. National Cancer Institute.