Breast MR false negatives vex researchers

MRI has proved more sensitive than mammography to detect certain types of breast cancer. Data from the International Breast MRI Consortium, reported at the RSNA meeting, confirm those findings but also indicate the potential for false negatives.

It's a troublesome finding, ac-cording to investigator Dr. David Bluemke, clinical director of MRI at Johns Hopkins.

"Many patients have ductal carcinoma in situ (DCIS) and microcalcifications, for which MRI is not needed, and a biopsy should just be performed if these are suspicious on the mammogram. We cannot underestimate the importance of mammographic screening," he said.

At this point, it could be technology and tumor type that prevent MRI from overriding a biopsy, said investigator Dr. Constance Lehman, director of breast imaging at the University of Washington, Seattle. In addition to DCIS, some types of low-grade infiltrating carcinomas do not enhance on MR.

"The standard approach to diagnosing cancer, the full diagnostic mammography workup with ultrasound and core biopsy, cannot be pushed aside in this era of MRI," she said.