Nearly 20 percent of patients with recently diagnosed breast cancer had additional malignant tumors found only by MRI, according to a study in the May issue of the American Journal of Roentgenology.

Amy M. Schell, MD, and colleagues from Dartmouth-Hitchcock Medical Center in Lebanon, N.H., undertook the study to evaluate the effect of preoperative breast MRI on the diagnosis of unsuspected additional malignant tumors and on surgical management choices in a non-investigational setting.

The researchers enrolled 199 patients newly diagnosed with breast cancer who underwent preoperative bilateral breast MRI. Data included additional imaging and biopsies performed, final surgical management and pathologic correlation. To reduce bias due to patient preference and variable surgical approaches, a surgeon blinded to final surgical treatment retrospectively reviewed ipsilateral malignant lesions found on breast MR images.

MRI detected additional suspicious tumors that were previously unsuspected lesions in 37 percent of the patients, according the authors. In 19 percent of the patients, they reported that 54 of these lesions were identified as malignant, of which 76 percent were invasive. A retrospective review of the MRI-identified ipsilateral malignant lesions resulted in hypothetical recommendations that would have altered the surgical treatment of 13 percent of the patients principally as mastectomy or wider excision.

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

For patients newly diagnosed with breast cancer, Schell and colleagues found that breast MRI in a mid-sized regional hospital depicts unsuspected malignant lesions in both the ipsilateral and contralateral breasts in proportions consistent with the results of earlier studies at larger institutions. "Whether clinical outcome is improved by changes in surgical management consequent to MRI detection of unsuspected malignant lesions remains unproven," the authors wrote.

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