Study may answer critics' fears about preop breast MRI

CHICAGO—Greater utilization of dynamic contrast-enhanced MRI at the University of California, San Diego, over a 6-year period helped improve surgery planning for tough breast cancer cases without hiking mastectomy rates, Christopher Comstock, MD, said in a presentation at RSNA 2007.

"Preoperative MRI has been shown in multiple studies to help change surgical management in a significant number of patients. However, some critics have raised concerns about the potential of preoperative MRI to increase mastectomy rates and cause delays in surgery, due to clinically insignificant disease detected by MRI," said Dr. Comstock, chief of breast imaging at UCSD.

Critics are less likely to cite lumpectomy's positive margin rates, which range from 30% to 40% nationwide and result in multiple surgeries to obtain clear margins, he said.

The study evaluated the effects of preoperative MRI on surgery in terms of delays and margins in patients with biopsy-proven breast cancer who underwent surgery at UCSD from 2000 to 2006. In the first 2 years of the study, only one patient had preoperative MRI. By the latter part of 2003, 40% to 50% of surgical patients were undergoing MRI.

The lumpectomy negative margin rate was higher for those who had preoperative MRI than for those who did not (80% vs 75%). "This may not seem like a big difference, but those who underwent preoperative MRI had larger or more complicated cancers or parenchymal patterns," Dr. Comstock said.

Lumpectomy negative margin rates reached 90% by 2006, a sign of better communication between radiologists and surgeons to maximize surgical outcomes and minimize delays, he said.

Despite increasing utilization of preoperative MRI, mastectomy rates remained stable throughout most of the study period. The results are partly a credit to the surgeons who used the MRI information wisely and counseled patients appropriately, Dr. Comstock said.

Furthermore, the researchers did not see a significant increase in the time to surgery for patients who underwent preoperative breast MRI, he said.