Abstract P2-13-04: The role of preoperative MRI in negative margins after breast conserving surgery in patients with invasive breast cancer or purely DCIS

Abstract

Abstract Introduction Clinical benefit of preoperative MRI in invasive breast cancer (IBC) patients and patients with purely ductal carcinoma-in-situ (DCIS) remains controversial. We aimed to study the role of preoperative MRI in negative margins after breast conserving surgery (BCS) and reexcision rate in a large population-based cohort. Methods Retrospective analyses were performed in women diagnosed with IBC and purely DCIS and surgically treated between 2011-2013 extracted from the Eindhoven Cancer Registry. Patients were excluded in case of: neo-adjuvant systemic therapy, (clinical or pathological) tumor stadium T4, distant metastasis, and unknown resection margin status. According to preoperative MRI use, the study population was divided into a non-MRI and MRI group. All multivariable analyses were adjusted for baseline differences between non-MRI and MRI group with P<0.1. No information was available on the exact reason to perform MRI preoperatively in these patients. Results A total of 3,116 patients were eligible of which 2,238 (71.8%) patients were treated by breast conserving surgery (BCS) and included for analyses. Preoperative MRI was performed in 592 (30.6%) IBC patients and 55 (18.3%) DCIS patients. In IBC patients, differences in non-MRI and MRI group were: median age (62 vs 58), histology (lobular type in 5.7% vs 24.5%), median tumor size (13 mm vs 15 mm), her2neu receptor status and specific tumor locations. Median (interquartile range) time between diagnosis and surgery in the non-MRI and MRI group were 21 (16-28) and 31 (22-40) days respectively (univariable and multivariable P<0.001). Negative margin was attained in 1,135 (84.4%) and 489 (82.6%) patients respectively (OR 0.88 95%CI 0.68-1.14 P=0.326). After adjustment for baseline differences and for factors associated with negative margin with P<0.1 (i.e. histology, tumor size, differentiation grade, progesterone receptor %, her2neu receptor status, regional lymph node stadium, and tumor location) MRI use was not associated with negative margin (OR 1.09 95%CI 0.81-1.45 P=0.587). Reexcision was performed in 96 (7.1%) and 62 (10.5%) patients (P=0.013). In case reexcision was needed, conversion to mastectomy occurred in 32 (2.4%) vs 20 (3.4%) patients (P=0.210). In patients with purely DCIS, only median age differed in non-MRI and MRI group (61 vs 57). Median (interquartile range) time between diagnosis and surgery in the non-MRI and MRI group were 22 (16-31) and 35 (23-49) days respectively (univariable P<0.001 and multivariable P=0.024). Negative margin was attained in 197 (80.1%) and 42 (76.4%) patients respectively (OR 0.80 95%CI 0.40-1.61 P=0.538). After adjustment for baseline differences and for factors associated with negative margin with P<0.1 (i.e. differentiation grade and tumor location) MRI use was not associated with negative margin (OR 1.51 95%CI 0.72-3.16 P=0.280). Reexcision was performed in 39 (15.9) and 10 (18.2) (P=0.672). In case reexcision was needed, conversion to mastectomy occurred in 12 (4.9%) vs 3 (5.5%) patients (P=0.859). Conclusion In both IBC and DCIS patients, preoperative MRI delayed time between diagnosis and surgery, but was not associated with a higher percentage of negative margins after BCS. Citation Format: Elvira L Vos, Adri C Voogd, Cornelis Verhoef, Inge-Marie Obdeijn, Linetta B Koppert. The role of preoperative MRI in negative margins after breast conserving surgery in patients with invasive breast cancer or purely DCIS [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P2-13-04.