MRI appears useful in detecting occult contralateral tumors in women recently diagnosed with breast cancer.
Women with a diagnosis of unilateral breast cancer have increased risk for developing cancer in the other breast. Investigators at 25 U.S. sites assessed the role of contralateral breast magnetic resonance imaging in women with recently diagnosed breast cancer who had had normal clinical and mammographic findings in the contralateral breast within 90 days of study enrollment. Contralateral breast MRI was performed no later than 2 months after diagnosis, and cancer status was followed for 1 year after the study MRI.
Of the 969 evaluable women (mean age, 53 years; 91% white; 80% with no family history of breast cancer), 121 women underwent recommended biopsies based on positive MRI findings. As a result, 30 tumors were detected, including 18 invasive carcinomas and 12 ductal carcinomas in situ (DCIS). Three additional contralateral breast cancers were diagnosed within 1 year of study entry. These three tumors, which represent false-negative MRI findings, were all DCIS (diameter range, 1–4 mm). The diagnostic yield of contralateral breast MRI was 3.1%, with an estimated sensitivity of 91% and a specificity of 88%. The negative predictive value of MRI was 99%, and the estimated positive predictive value was 21%.
Comment: In this landmark study, the estimated risk for detection of contralateral breast cancer 1 year after a negative breast MRI was well under 1%, and the few contralateral tumors to be detected at that time were small and contained. Thus, for a woman recently diagnosed with unilateral breast cancer and considering contralateral prophylactic mastectomy, negative MRI findings might provide sufficient reassurance to forgo this surgery. An editorialist notes that the American Cancer Society now recommends breast MRI for women with a 20% or greater lifetime risk for breast cancer. The ACS also states that there is insufficient evidence to make a recommendation for or against MRI screening for women with a personal history of breast cancer or for those with radiologically dense breasts (CA Cancer J Clin 2003; 53:141). As breast MRI becomes more widely available, clinicians and patients should recognize that the quality of such examinations varies widely. Furthermore, some facilities offer breast MRI but lack the means to perform biopsies of abnormalities detected with this technology. The ACS guidelines recommend that breast MRI should not be performed in this setting.
— Andrew M. Kaunitz, MD
Published in Journal Watch Women's Health March 29, 2007
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