(American Roentgen Ray Society) -- Some breast cancer patients who undergo a lumpectomy should then be considered for an MR examination because MR is an accurate way to look for any disease left in the breast, two new studies show. Information on residual disease is vital in determining the best treatment for these women.

In one study, radiologists reviewed 100 patients who had undergone a lumpectomy, whereby the tumor and closely surrounding areas were removed. When the tumor specimen was looked at under a microscope it showed that the cancer had spread to or near the edge (margins) of the specimen.

These women then had an MR examination to look for any residual disease, says Elizabeth Morris, MD, a radiologist at Memorial Sloan Kettering Cancer Center in New York, and lead author of the study. Fifty-eight of the women had disease left over after lumpectomy, says Dr. Morris. Overall, MR imaging identified 86% of residual disease, she says. "It was most accurate (90%) in identifying residual disease that was in a different quadrant than the lumpectomy site; it was least accurate (78%) in identifying unifocal residual disease, that is disease that was within 2 cm of the lumpectomy site," Dr. Morris says.

A separate study of 22 women (23 breasts) with ductal carcinoma in situ confirms Dr. Morris' numbers. In the study, "MR imaging identified residual disease near the lumpectomy site in 18 of the 23 breasts (78%)," says Jennifer Menell, MD, clinical assistant radiologist at Memorial Sloan Kettering Cancer Center.

Nine of the women also had a mammogram, adds Dr. Menell. MR was able to identify residual disease in seven of these nine patients, while mammography was only able to identify residual disease in six patients.

Not all of the patients in this study had positive margins, notes Dr. Menell. Two of the patients had the radiologic examination following lumpectomy to determine the extent of disease.

Two patients had surgery outside of Memorial Sloan Kettering Cancer Center, and information on whether they had positive margins or not wasn't available, says Dr. Menell.

"MR imaging provides us with a window to the breast that we haven't had before and maps out for us how extensive the disease really is," says Dr. Morris. "If tumor extent can be accurately gauged, appropriate treatment can be planned," adds Dr. Menell.

Dr. Menell and Dr. Morris will present their studies on May 7 during the American Roentgen Ray Society Annual Meeting in San Diego.