An increasing number of women are treating their breast cancer with brachytherapy, a type of radiation therapy that delivers a smaller, more targeted dose of radiation.

But a new study suggests that the treatment might  increase the likelihood that a woman's breast would need to be removed, and that the therapy  may cause more complications after treatment.

Doctors say the findings don't condemn the treatment but do give doctors and patients something  to think about when selecting appropriate treatments for breast cancer.

Researchers from M.D. Anderson Cancer Center in Houston studied the Medicare records of more than 92,000 women age 67 and older whose invasive breast cancer had been treated with a lumpectomy and a subsequent course of radiation.  Of those women, almost 86,000 received whole-breast irradiation and nearly 7,000 received brachytherapy.

When it came to survival after breast cancer, there was  no difference  between the two groups. But women who received brachytherapy were more likely to need a mastectomy within five years of their treatment. Four percent of the women who got brachytherapy got a mastectomy within five years compared with 2 percent of women who received whole-breast irradiation.

Women who received brachytherapy also had more complications,  such as breast pain and rib fractures, after treatment.

 Dr. Ben Smith, the study's author and an assistant professor of radiation oncology at M.D. Anderson, acknowledged the difference in mastectomy rates between the two groups was slight, but said the data gave the best information so far on the differences.

"Our findings mean that some of the tradeoffs between brachytherapy and whole-breast irradiation may be more complex than initially appreciated," Smith said.

The study, published today in the Journal of the American Medical Association, is the first to compare the effectiveness of brachytherapy with whole-breast irradiation.

In brachytherapy, also called accelerated partial breast irradiation, doctors use a catheter to deliver radiation to a specific area rather than delivering the radiation to the entire breast. It's a more targeted way to treat the cancer and takes far less time - women can complete brachytherapy in about one week compared with the average of six weeks needed for whole-breast radiation.

With time and convenience on its side, brachytherapy has become increasingly popular in the past decade. In 2007, about 13 percent of breast cancer patients received it as their only treatment, up from about 4 percent in 2003.

However, so far, no large clinical trials have compared brachytherapy with whole-breast irradiation to test which  is more effective.

Many doctors have worried that targeting only a small portion of breast tissue with radiation might miss cancer cells lurking elsewhere in the breast that could develop into cancer later on.

"Whole breast irradiation effectively treats those areas as well," said Dr. Len Lichtenfeld, deputy chief medical officer of the American Cancer Society. "The question has always been whether the use of these newer techniques has that same benefit of treating those silent areas that we know exist in other parts of the breast."

Smith said the results of his study didn't mean that brachytherapy was a dangerous or inappropriate treatment. Instead, patients and doctors should consider the findings when choosing the best course of treatment.

Doctors said much more research on brachytherapy was needed, including the results of an ongoing clinical trial comparing the treatment with whole-breast irradiation.

"The final answer on the appropriate use of brachytherapy is not yet in," said Dr. Stephen Edge, chairman of breast and soft tissue surgery at Roswell Park Cancer Institute in Buffalo, N.Y.