Abstract P3-02-12: Impact of magnetic resonance imaging on conversion from wide local excision to mastectomy in patients with ductal carcinoma in situ: First results from the ECOG-ACRIN 4112 prospective study

Abstract

Abstract Purpose: To estimate the proportion of patients with ductal carcinoma in situ (DCIS) judged to be candidates for wide local excision (WLE) based on mammography (+/- sonography) and clinical exam who: (A) convert from WLE to mastectomy as the first surgical procedure based on magnetic resonance imaging (MRI) findings, and (B) have a mastectomy as the final surgical procedure. Patients and Methods: The study population included women with DCIS diagnosed by core needle biopsy (and no evidence of invasive or micro-invasive disease) judged to be candidates for WLE by their surgeon based on standard imaging (mammogram +/-sonography) and clinical exam without prior breast MRI. After registration bilateral contrast enhanced breast MRI was performed, and a protocol management algorithm was followed. Before and after MRI, the surgeon documented the planned surgical procedure, including reason for conversion from WLE to mastectomy if the surgical plan changed. Prior evidence suggests that about 8-12% of patients initially considered candidates for WLE based on mammography ultimately require mastectomy, and the addition of MRI increases the likelihood of mastectomy by about 1.5-fold. A sample size of 350 (332 evaluable) was planned to ensure a 95% confidence interval (C.I.) of 8% if the actual mastectomy conversion rate was as high as 16%. Two-sided 95% Wilson confidence interval for proportion of patients converting to mastectomy based on MRI was derived. Results: Of 363 patients enrolled, 340 had sufficient information to assess aim A (conversion to mastectomy after MRI), and 322 for aim B (mastectomy as final surgical procedure). At study entry, median age (range) was 59 years (34-87). Features of DCIS lesions included: median longest diameter (range) 11 mm (1-100); ER positivity 76.2%; low, intermediate and high grade 15.9%, 40.9% and 39.4% respectively (3.8% unknown). Based on MRI findings (Aim A), mastectomy rather than WLE was recommended as the first surgical procedure in 25/340 (7.4%, 95% CI: 5.0%, 10.6%). Reasons included large lesion size (N=15), multi-centric disease (N=6), and contralateral disease prompting bilateral mastectomy (N=4). An additional 28/340 (8.2%) converted to mastectomy as the first surgery based on other factors, including patient preference (N=25), interval discovery of genetic mutation (N=2), or inability to receive radiation treatment (N=1). Of the 278 patients for whom initial WLE was performed after MRI, 10/278 (3.7%) converted to mastectomy, all due to positive or close (< 2 mm) surgical margins. Overall (Aim B), 62/322 (19.3%, 95% CI 15.3%, 23.9%) had mastectomy as the final surgical procedure. Conclusion: In women with DCIS judged to be candidates for WLE based on mammography (+/- sonography), conversion to mastectomy is fairly common with nearly 1 in 5 patients ultimately undergoing mastectomy. Breast MRI findings account for less than half of the conversions to mastectomy. For patients who remained candidates for WLE after MRI, 96.3% achieve successful WLE as the final surgical procedure. Citation Format: Lehman CD, Gatsonis C, Greco E, Khan SA, Sparano JA, Solin LJ, Badve SS, Corsetti RL, Rahbar H, Spell DW, Blankstein KB, Han LK, Sabol JL, Bumberry JR, Miller KD, Comstock C. Impact of magnetic resonance imaging on conversion from wide local excision to mastectomy in patients with ductal carcinoma in situ: First results from the ECOG-ACRIN 4112 prospective study [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P3-02-12.