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Proceed with Caution: MRI Evaluation in Women with New Breast Cancer

MRI detected occult contralateral cancers in 3% of women, but 10% received false-positive results that led to biopsies.

Detecting a second breast cancer in a woman with unilateral breast cancer is an ongoing concern. Even when mammogram results are normal, as many as 10% of women with unilateral breast cancer will develop cancer in the contralateral breast. In an American College of Radiology Imaging Network (ACRIN) study, researchers evaluated the role of contralateral breast magnetic resonance imaging in 969 women with new diagnoses of breast cancer. Contralateral mammograms were normal in all patients. MRIs were performed within 60 days of first breast cancer diagnoses.

Of 121 positive MRI results, contralateral breast cancers were verified by tissue diagnoses in 30 women (3.1% of patients; 18 invasive carcinomas and 12 ductal carcinomas in situ [DCIS]). The mean diameter of invasive carcinomas was 10.9 mm. No patient had axillary metastases. Biopsies were performed to rule out mammographically occult contralateral breast cancer in 12.5% of all patients. The false-negative rate for detecting contralateral breast cancer with MRI was 10.9%.

Comment: For a patient who develops subsequent contralateral breast cancer after a diagnosis of unilateral breast cancer, the index breast cancer generally determines the patient’s prognosis when she is followed by routine clinical examination and yearly contralateral diagnostic mammography. Of note, small occult contralateral breast cancers can be eradicated if a patient receives chemotherapy, endocrine therapy, or both. Although MRI of the contralateral breast can detect clinically and radiographically occult breast cancer when performed near the date of the initial cancer diagnosis, no evidence shows that early contralateral breast MRI will lead to a survival advantage. In this study, no survival advantage would be expected for the 12 patients with contralateral DCIS only. Based on MRI results in this study, more than 10% of women required biopsy procedures; however, 97 of every 100 women who were evaluated indeed did not have contralateral breast cancer.

The practice of ordering contralateral breast MRIs in patients with unilateral breast cancer likely would engender a high rate of unnecessary biopsies, and even contralateral mastectomies, if such studies were performed in the community by radiology groups that were not experienced with this technique and that did not have specific guidelines for exactly how an abnormal breast MRI image should look. At this point, general adoption of this practice in the U.S. likely would not benefit our patients and potentially could be dangerous. Widespread adoption of accreditation and appropriate guidelines for this emerging technique are necessary.

— Henry Mark Kuerer, MD, PhD, FACS

Published in Journal Watch Oncology and Hematology March 28, 2007

Citation(s):

Lehman CD et al. MRI evaluation of the contralateral breast in women with recently diagnosed breast cancer. N Engl J Med 2007 Mar 29; 356:1295-303.

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