TUESDAY, March 18 (HealthDay News) -- Freezing the prostate to kill cancer, a procedure called cryotherapy, may be as effective as more common treatments such as radiation, U.S. researchers report in the first such follow-up study spanning 10 years.

In this procedure, thin needles are placed into the prostate through which super-cooled argon gas is circulated -- reducing the temperature to up to -150 degrees centigrade. The technique freezes the prostate, killing the cancer it contains.

But the method remains controversial, and is currently the least-used method for treating prostate cancer in the United States.

"One of the reasons cryotherapy is controversial is we didn't know the long-term results," said study co-author Dr. Ralph Miller, director of the prostate center at the Allegheny General Hospital in Pittsburgh. "It really takes 10 years of good follow-up before you can tell how well a treatment works, because prostate cancer typically grows slowly," he said.

The 10-year follow-up study is the first of its kind, Miller noted. It found that clinical outcomes "are basically the same as seed implant radiation and external radiation therapy, the other minimally invasive therapies," he said.

Miller's team reviewed the cases of 370 men who underwent cryotherapy as first-line treatment for various stages of prostate cancer, according to the report in the March issue of Urology.

During an average of 12.5 years of follow-up, the researchers found that men with low-risk prostate cancer had a nearly 81 percent disease-free survival rate after undergoing cryotherapy. In addition, more than 74 percent of men with moderate-risk prostate cancer and almost 46 percent of men with high-risk malignancies experienced disease-free survival over the long follow-up period.

"These findings are confirmation that cryotherapy is another viable treatment option for prostate cancer," Miller said. "There are probably 10- to 15,000 of these procedures done each year in the United States," he noted.

More than 60,000 prostate surgeries are performed in the U.S. each year and some 50,000 men receive implanted radiation. About 30,000 men will also undergo external radiation for prostate cancer, according to Dr. Nelson Neal Stone, a clinical professor of urology and radiation oncology at Mount Sinai School of Medicine in New York City.

Men trying to decide which treatment is best for them may now also want to consider cryotherapy, knowing that the results will be similar to other choices, Miller said. Patients can turn to cryotherapy after failing radiation therapy, he noted.

Cryotherapy may also be a good option for patients who are likely to fail radiation therapy or for those who have a prostate obstruction that causes them trouble urinating, he added.

In addition, patients with advanced prostate cancer may also benefit from cryotherapy in lieu of radiation, Miller said. "For some patients it's a good first choice," he said.

According to Miller, cryotherapy is offered at a number of hospitals around the country but it is not as common as radiation and surgery.

Risks associated with cryotherapy are the same as those of other prostate cancer treatments and include incontinence, impotence and not being cured, Miller said.

One expert was more skeptical, however.

"While it's very good that this study has long follow-up and the results look reasonable, there is no way to know how the results really compare to any standard treatment like surgery or radiation therapy -- this is not a randomized trial," noted Dr. Anthony D'Amico, the chief of radiation oncology at Brigham and Women's Hospital in Boston.

In a randomized trial, patients are randomly sent to receive one treatment or another, and the outcomes are then directly compared. The only way you can really tell if cryotherapy is as good as more conventional treatments is in this type of head-to-head comparison, D'Amico said.

"I don't want people to say that cryotherapy is equivalent to surgery or radiation and should be used as primary treatment for men with localized prostate cancer," he said. "Before one would adopt this treatment you really need a randomized trial because I would have to be convinced that it was as good as surgery or radiation for me to want to adopt it -- I think it's still experimental."

More information

For more information on prostate cancer, visit the U.S. National Cancer Institute.