Breast magnetic resonance imaging helps doctors select best treatment for early breast cancers

Breast magnetic resonance imaging enhances patient selection for accelerated, partial breast irradiation by detecting previously unsuspected, microscopic lesions within the breast, according to a study presented October 17, 2005, at the American Society for Therapeutic Radiology and Oncology's 47th Annual Meeting in Denver.

The study shows that almost 10 percent of patients who had a breast MRI before completing breast conservation treatment had additional disease that was previously not seen on the patient's mammogram (breast X-ray).

For patients with early stage breast cancer, the current standard treatment involves surgery to remove the tumor (lumpectomy) followed by a course of external beam radiation to the entire breast over a six to seven week period to kill any remaining cancer cells. Alternatively, radiation oncologists are studying accelerated partial breast irradiation, which reduces the radiation course to just one to five days for a select group of women with early-stage breast cancer.

In this study, doctors performed not only standard mammography, but also breast MRI in order to determine as accurately as possible the extent of the patient's tumor, as well as the presence of any unsuspected disease elsewhere in the breast. Of the 51 patients reported, almost 10 percent had additional cancer identified on the MRI that was not appreciated on the mammogram. This additional disease meant the patients were perhaps more safely treated with wider removal of breast tissue followed by whole breast radiation therapy, or mastectomy (surgical removal of the breast) in cases of biopsy-proven multicentric disease.

"At this point, we feel that partial breast irradiation is best reserved for women with unifocal carcinoma, excised with tumor-free margins, without evidence of multifocal or multicentric disease. Breast MRI may help radiation oncologists identify the most suitable candidates for this accelerated treatment to minimize the chance that a woman's cancer will return near the original tumor or elsewhere in the breast," said Kathleen Horst, M.D., lead author of the study and a radiation oncologist at the Stanford Cancer Center in Stanford, California.