Preoperative Breast Magnetic Resonance Imaging in Women With Local Ductal Carcinoma in Situ to Optimize Surgical Outcomes: Results From the Randomized Phase III Trial IRCIS.

We evaluated the addition of breast magnetic resonance imaging (MRI) to standard radiologic evaluation on the re-intervention rate in women with ductal carcinoma in situ (DCIS) undergoing breast-conserving surgery. Women with biopsy-proven DCIS corresponding to a unifocal microcalcification cluster or a mass less than 30 mm were randomly assigned to undergo MRI or standard evaluation. The primary end point was the re-intervention rate for positive or close margins (< 2 mm) in the 6 months after randomization ( ClinicalTrials.gov identifier: NCT01112254). A total of 360 patients from 10 hospitals in France were included in the study. Of the 352 analyzable patients, 178 were randomly assigned to the MRI arm, and 174 were assigned to the control arm. In the intent-to-treat analysis, 82 of 345 patients with the assessable end point were reoperated for positive or close margins within 6 months, resulting in a re-intervention rate of 20% (35 of 173) in the MRI arm and 27% (47 of 172) in the control arm. The absolute difference of 7% (95% CI, -2% to 16%) corresponded to a relative reduction of 26% (stratified odds ratio, 0.68; 95% CI, 0.41 to 1.1; P = .13). When considering only the per-protocol population with an assessable end point, the difference was 9% (stratified odds ratio, 0.59; 95% CI, 0.35 to 1.0; P = .05). Total mastectomy rates were 18% (31 of 176) in the MRI arm and 17% (30 of 173) in the control arm (stratified P = .93). For 100 lesions seen on MRI, nonmass-like enhancement was more predominant (82%) than mass enhancement (20%). Nevertheless, no specific morphologic and kinetic parameters for DCIS were identified. The study did not show sufficient surgical improvement with the use of preoperative MRI to be clinically relevant in DCIS staging. However, this could be reconsidered with the improvement of new MRI sequences and new modalities in magnetic resonance techniques.