In newly diagnosed breast cancer, is a contralateral prophylactic mastectomy necessary following a negative MRI?

Abstract

627 Background: With more centers using MRI to aid in initial staging, there is apprehension that the highly sensitive MRI exam may lead to “unnecessary” mastectomies. We evaluated whether a negative contralateral MRI could be used to rule out a synchronous contralateral carcinoma and hence avoid a prophylactic contralateral mastectomy (CPM) at initial breast cancer diagnosis. Methods: Data of women with a new diagnosis of breast cancer (invasive or DCIS) from February 2003-November 2007 at our institution were reviewed. Women who had a negative MRI of the contralateral breast and who subsequently underwent CPM were included. A CPM was one in which there was no histological confirmation of cancer in the contralateral breast before surgery. All mastectomy specimens were analyzed pathologically. True negatives were mastectomy samples which contained no cancer following pathologic examination. False negatives were mastectomy samples which were found to have cancer after pathologic review. Results: 538 women were identified. 51 women met the study criteria. Median patient age was 56 years (range, 33–77). Of the 51 women who underwent a CPM, 2 were found to have pathologic confirmation of cancer. One occult cancer was a 0.3 cm grade 1, invasive lobular carcinoma; the second a 0.5 cm, low grade DCIS. The overall prevalence of synchronous occult contralateral cancer after a negative MRI was 3.9% (95% CI 0.5 - 13.5%). The negative predictive value of MRI was 96.1% (95% CI 86.5 - 99.5%). Conclusions: This study provides pathologic data regarding the utility of a negative contralateral breast MRI in women with newly diagnosed breast cancer. The prevalence of a synchronous occult contralateral cancer after a negative MRI in women with newly diagnosed breast cancer is very low. Physicians and patients can be assured that the risk of occult cancer is low in the setting of a normal contralateral MRI, an important fact when considering CPM after a diagnosis of unilateral breast cancer. No significant financial relationships to disclose.