A new radiation treatment for breast cancer is becoming increasingly popular despite lack of good evidence, at least among well-insured Medicare patients, U.S. researchers say.

According to claims data, use of the therapy, which irradiates only a portion of the breast instead of standard whole-breast radiation after lumpectomy, climbed more than 10-fold for those patients between 2001 and 2006.

While gold-standard clinical trials of the newer treatment are still missing, two other events did coincide with steep increases in its use: approval of a device used to deliver the radiation in 2002 and Medicare reimbursement in 2004.

“It brings to the front the issue of when we should enact a new technology,” said Dr. David J. Sher, an expert in radiation treatment, who was not involved in the new study. “What the paper shows it that it really is done in the absence of evidence.”

The National Cancer Institute says that more than 200,000 American women will get breast cancer in 2010 and about a fifth will die from the disease.

After lumpectomy, up to 40 percent of women see the cancer return, but that number can be reduced to about 10 percent with external-beam radiation of the whole breast. Common side effects are swelling and redness.

In contrast to whole-breast radiation, which usually takes several weeks to complete, the new partial-breast treatment lasts less than one week.

One example of the so-called brachytherapy approach is MammoSite, a device marketed by Massachusetts-based Hologic, and used on more than 50,000 women so far, according to the company.

It consists of a small balloon, which is inflated in the cavity left behind after the tumor is removed. The balloon then delivers high-dose radiation to the parts of the breast most likely to develop new cancers.

Although the idea is promising, Sher said, there aren’t any large studies that have compared whole-breast radiation to this treatment. He said one such study was ongoing, but in the meantime, both efficacy and side effects were up in the air.

The new findings, published in the Journal of Clinical Oncology, are based on data for nearly 7,000 older women who had radiation treatment after having a breast tumor removed. All had private health insurance in addition to Medicare.

Ya-Chen T. Shih of the University of Texas MD Anderson Cancer Center and her colleagues found that from 2001 to 2006, the use of partial-breast radiation alone after breast surgery rose steadily from less than one percent of cases to 10 percent, at the expense of whole breast radiation.

It appeared that wealthier women were more likely to get the new treatment, the researchers found, and it is unclear if the results extend to other women.

In an earlier study comparing the cost-effectiveness of different radiation treatments, Sher found MammoSite was unlikely to be cost-effective compared to whole-breast radiation. “MammoSite is significantly more expensive,” he said.

According to Shih, whole-breast radiation therapy costs about $13,000 and breast brachytherapy about $23,400.

Hologic could not provide comments by deadline.

Until more evidence becomes available, Sher said, “women should know that the standard of care in managing (cancer of the) breasts is whole-breast radiation.”

“There are tens of thousands of women who have been treated with whole-breast radiation and they have done very well,” he added.

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SOURCE: Journal of Clinical Oncology, online December 10, 2010