Magnetic resonance imaging versus mammography for diagnosing ductal carcinoma in situ

Abstract

1504 Background: Mammographic screening is considered the mainstay for diagnosing pre-invasive breast cancer (DCIS). However, (over)diagnosis of DCIS has become a major concern. We investigated the sensitivities of high-resolution MRI and of state-of-the-art mammography (Mx) for diagnosing pure DCIS, and compared the biologic profile of MRI-detected versus Mx-detected DCIS. Methods: Prospective study on 5960 consecutive women who were referred to a dedicated breast unit for screening or for diagnostic assessment. Women underwent bilateral mammography with at least 2 views, plus spot compression views where appropriate, and high-resolution bilateral MRI. A total 137 women received the final pathologic diagnosis of having DCIS (no invasion). Of these, 108 (79%) had been referred for regular screening, 14 (10%) for high risk screening, 10 (7%) for follow up after breast cancer, and 5 (4%) for clinical symptoms. We investigated the mode of detection, and the biologic profile of the DCIS (size, nuclear grading, ER/PR and HER2-receptor status). Results: Overall, Mx was positive in 79/137 patients (58%), MRI was positive in 123/137 (90%). In 68/137 (50%), Mx and MRI were concordantly positive. In 3/137 (2%), Mx and MRI were both false-negative. In 11/137 (8%), only Mx was positive, MRI was false- negative. In 55/137 (40%), only MRI was positive, Mx was false negative. Of the 11 DCIS which were only detected by Mx, 1 was high grade, none was ER negative or HER2 positive. Mean VNPI was 4.2. Of the 55 DCIS which were only MRI detected, 41 (78%) were high grade, 14 (27%) were ER negative, 17(33%) HER-2 positive. Mean VNPI was 6.5. Conclusions: Compared to mammography, MRI offers a significantly higher sensitivity for DCIS, in particular for DCIS with adverse biologic profile: Half of the high grade or HER2-positive DCIS were only MRI detected. In turn, DCIS which was only mammography detected had a relatively benign biologic profile. We propose that MRI is helpful for diagnosing biologically (i.e. possibly prognostically) relevant DCIS [Table: see text] No significant financial relationships to disclose.