Researchers report that a magnetic resonance imaging (MRI) scan can locate lesions that are not seen on mammography of the breast in women who are candidates for accelerated, partial breast irradiation after lumpectomy.

"In some cases, the findings we saw with the MRI changed our decision on managing the patients," said Kathleen Horst, MD, Clinical Instructor in Radiation Oncology, Stanford Cancer Center, California, United States.

Dr. Horst described her findings in an oral presentation here on October 17^th at the 47^th annual meeting of the American Society for Therapeutic Radiation and Oncology (ASTRO).

When standard breast conserving surgery is performed, she said, the entire breast is irradiated. "We believe that what we are doing with whole breast irradiation is destroying microscopic or small tumors that were missed in mammography," Dr. Horst said.

But in accelerated, partial breast irradiation only the area immediately surrounding the tumor bed receives intense radiation. As part of an experimental procedure, Dr. Horst and colleagues used MRI to scan the breast to see if the procedure might be useful as a back-up scan for women who were not getting a full breast radiation procedure.

The researchers performed MRI scans in 51 women who were candidates for accelerated partial breast irradiation. In 41 of the women, the scans found nothing remarkable. In the other 10 there were suspicious findings, Dr. Horst said. Five of those cases were benign, but five other cases had cancers that had not been detected by mammography. These women underwent wider excision and in three of these, the extent of disease or the patients' decision resulted in the decision to perform a mastectomy.

Dr. Horst said the results of this study are preliminary and should not be considered as a justification for using MRI as back-up to accelerated partial breast irradiation.

"Breast MRI may help radiation oncologists identify the most suitable candidates for the accelerated treatment to minimize the chance that a woman/s cancer will return near the original tumor or elsewhere in the breast," she said.