MRI: Not Useful Before Breast Biopsy

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Summary and Comment

MRI: Not Useful Before Breast Biopsy

In this study, MRI's negative predictive value was 85% -- not high enough to omit biopsy when other parameters suggest malignancy.

In a recent study sponsored by the National Cancer Institute, researchers assessed whether magnetic resonance imaging prior to breast biopsy is useful as an adjunct to conventional cancer-detection methods. The study sample comprised 821 women (mean age, 53) who were referred for biopsy based on the following: mammogram results suspicious for or highly suggestive of malignancy (BI-RADS score of 4 or 5; 84.7% of participants), palpable breast abnormality (11.7%), other physical examination abnormality such as nipple discharge (1.8%), or abnormal ultrasound with normal mammogram (1.8%). Participants had no history of cancer in the affected breast.

Index lesions were defined as the palpable, ultrasonographic, or mammographic findings that were the basis for biopsy referral. Of 404 malignant index lesions, 341 were invasive cancer and 63 were ductal carcinoma in situ. MRI identified 356 of these lesions as malignant (sensitivity, 88.1%). The positive predictive value of MRI was 72.4%, which was significantly higher than that observed for mammography (52.8%). Of the 417 participants without malignancy, MRI was negative for malignancy in 281 (specificity, 67.4%). Of 329 women with MRIs negative for malignancy, no malignancy was found on biopsy in 281 (negative predictive value, 85.4%).

Comment: As other data have recently shown (Journal Watch Women's Health Sep 9 2004 and Nov 23 2004), these findings confirm MRI's high sensitivity and relatively low specificity when used to screen for breast cancer. However, this study's goal was to assess MRI's usefulness not as a screening tool but rather as an adjunctive imaging procedure prior to breast biopsy. Based on these results, the negative predictive value of MRI (85.4%) is not high enough for women with negative MRIs to forgo biopsy when other parameters (e.g., a suspicious mammogram) suggest malignancy.

— Andrew M. Kaunitz, MD

Published in Journal Watch Women's Health January 25, 2005