The 82-year-old, who lives about an hour's drive from Brigham and Women's Hospital in Boston, could get regular radiation treatments, which would require her to be in Boston five days a week for seven weeks. Or she could opt for a new type of radiation that requires only 10 treatments—given twice a day for five days. In the standard method, the whole breast is irradiated; in the new one, radiation is aimed at only the tumor's former location.

Desilets chose the latter, and went shopping every day between the first and second treatment. "It was a piece of cake," she said. "I highly recommend it. I felt great the whole time."

More than half of women with relatively small tumors opt to skip a lumpectomy and instead have their entire breast removed—usually to avoid radiation. Because radiation requires regular treatments for weeks and has side effects including skin irritation, it creates enormous difficulties for those who live far from medical centers or whose work schedules make it difficult to spend part of every day getting treatment.

But the new procedure, called accelerated partial breast radiation, could change the outcome of such decisions. Although many insurers already pay for the procedure, it's too soon to say whether the new technique is ready to replace the old, which is supported by decades of practice and studies. An estimated 71 000 women each year may be potential candidates for the treatment, which is available at many medical centers because of growing patient demand.

"The quandary is that the rationale for partial breast irradiation is compelling, but we are moving away from something that is tried and true with excellent long-term results to something that has at least something of a question mark," said Dr. Jay Harris, chief of the department of radiation oncology at Brigham and Women's Hospital and the Dana-Farber Cancer Institute.

On the other hand, the risk of the new approach is probably small. When cancer returns to a breast, it almost always does so in the initial tumor site, not in a more distant part of the breast, said Dr. Phillip Devlin, director of brachytherapy at Brigham and Women's Hospital and the Dana-Farber Cancer Institute. That suggests tightly targeted radiation should do the trick.

Because of its newness, partial breast irradiation is generally recommended specifically for women with small tumors in only one section of the breast and no signs of cancer in the lymph nodes. For Desilets, the new radiation was a breeze. "I didn't feel anything. My skin didn't get red. There were no repercussions at all."