Abstract PS1-36: Outcomes and management of positive and close anterior margins following skin-sparing mastectomy

Abstract

Background: Skin-sparing mastectomy (SSM) has emerged as a safe oncologic technique for extirpation of breast tissue in the context of immediate breast reconstruction (IBR). Documented rates of local recurrence are comparable for SSM and conventional mastectomy and attention to the plane of dissection is essential with removal of skin overlying the tumor when clinically indicated. The incidence of positive or close margins is greatest for peripheral tumors at the breast boundaries and will influence rates of local recurrence. Management of positive or close margins is inconsistent and this audit aimed to determine the incidence of compromised margins and their impact on local recurrence and overall survival in SSM patients. Methods: A retrospective analysis was undertaken of breast patients with invasive or non-invasive breast cancer undergoing SSM and IBR at a single tertiary referral centre between January 2006 and December 2009. A total of 150 patients were included and all underwent resection of breast tissue with a peri-areolar incision. Clinical information was extracted from a prospectively maintained database. Data was collected on patient demographics, tumor characteristics, non-surgical treatment and outcome events (recurrence and death). The definition of a negative margin on histology during the study period was tumor ≥2mm from the edge of the specimen with close margins <2mm but no ink on tumor. Results: The mean age of patients was 51 years (range 24 - 75) and median duration of follow up 140 months (range 10 - 167). Amongst these 150 SSM patients, 25 (17%) had positive or close anterior margins (<2mm) with 125 patients having negative anterior margins (>2mm). None of these patients with close or positive margins underwent re-excision following initial SSM. Twenty-four patients (16%) developed either loco-regional (n=9) or distant recurrence (n=15) with 126 patients (84%) alive at 10 years. Although more patients with positive/close compared with negative margins had recurrence (20% versus 15%), this did not reach statistical significance (p=0.55) Similar proportions of patients in each margin category received post-mastectomy radiotherapy (p=0.66) and adjuvant/neo-adjuvant chemotherapy (p=0.66). There were no statistically significant differences in rates of local recurrence or survival between patients with positive/close and negative margins but the number of events is small and may represent a type II error. Conclusion: Twenty percent of patients (5/25) with positive or close margins after SSM develop local or distant recurrence with reduction of risk by PMRT of <50%. None of the patients with positive/close margins who developed recurrence survived for 10 years. Close/positive margins after SSM may portend a worse outcome from recurrent disease and further research is required to optimize management of this group of patients in an era of skin-preserving mastectomy. Citation Format: Primeera Wignarajah, Dorin Dumitru, John R Benson. Outcomes and management of positive and close anterior margins following skin-sparing mastectomy [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS1-36.