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MRI Detects "Unsuspected" Breast Cancers

June 3, 2009

Dr. Lewis

Petra J. Lewis, MB, BS

Nearly 20 percent of patients with recently diagnosed breast cancer had additional malignant tumors found only by MRI (magnetic resonance imaging), according to a recent study performed at Dartmouth-Hitchcock Medical Center (DHMC) and published in the May edition of the American Journal of Roentgenology (AJR).

Breast MRI is increasingly being used for the preoperative evaluation of patients with newly diagnosed breast cancer. In this study, a total of 199 patients with newly diagnosed breast cancer underwent breast MRI. The participants' ages ranged from 26-85 years with a median age of 57 years.

"We found additional, unsuspected cancers in the ipsilateral breast (the one that had already been diagnosed with cancer) in 16 percent of patients and we found cancers in the contralateral breast (the one that had not been diagnosed with cancer) in 4 percent of patients," said Petra J. Lewis, MB, BS, the study's lead author. "These patients had already had bilateral mammography and these tumors had not been apparent on mammography," said Dr. Lewis.

In studies in which the comparison has been made, breast MRI appears to depict more malignant lesions than either mammography or ultrasound.

"The detection of an unsuspected tumor is critical. These additional tumors in nearly a fifth of patients are tumors that can potentially grow and not be diagnosed until they are much larger-affecting the health and survival of the patients," said Dr. Lewis.

In studies in which the comparison has been made, breast MRI appears to depict more malignant lesions than either mammography or ultrasound.

The routine use of preoperative breast MRI has not been without controversy, however. The authors acknowledge that the false-positive rate of MRI can be high and varies markedly among previous studies. In addition, the interpretation of breast MR images can be difficult and has a significant learning curve. The study also raises the question of whether the results obtained at centers with extensive experience in breast MRI can be extended to centers with less experience.

The study notes that while there appears to be a substantial positive effect on patient care, the cost-effectiveness of breast MRI and its overall effect on patient survival warrant further study. The authors also say that the emotional as well as financial impact to the patient must be considered, in that delays caused by additional testing can increase patient anxiety.

"This study has been particularly helpful to us as clinicians because it gives us data we can discuss with patients when recommending breast MRI," Lewis said.

The study's authors are Petra J. Lewis, MB, BS, Department of Radiology; Amy M. Schell, MD, Department of Medicine, and Kari Rosenkranz, MD, Department of Surgery, Dartmouth Hitchcock Medical Center. Both Dr. Lewis and Dr. Rosenkranz are members of Norris Cotton Cancer Center's Comprehensive Breast Program.