Abstract PO1-23-07: The effect of intra-operative margin assessment during breast conserving surgery for breast cancer in a Dutch cohort

Abstract Background Pre-operative tumour localisation and intraoperative specimen radiography are necessary to perform adequate resection of non-palpable breast tumours. Intraoperative digital specimen mammography (IDSM), is an alternative to conventional specimen radiography (CSR) and has the benefit of providing immediate specimen evaluation and the potential of decreasing operation time. IDSM may also reduce positive margins and re-excision rates. IDSM was implemented in our hospital in 2018. The study objective was to evaluate the surgery time, radicality and re-excisions in IDSM and CSR. Methods A single centre retrospective cohort study with two cohorts: CSR (n=532) and IDSM (n=475). The primary outcome was duration of surgery. Secondary outcomes were margin status of the primary surgery, the perioperative cavity shave rate and the re-excision rate. Differences between cohorts were compared using univariate statistics and multiple regression to adjust for variables that were statistically significantly associated with duration of surgery. Results IDSM use was associated with 8 minutes shorter surgery time (B -8.242, p < 0.001). Treatment variables independently associated with the duration of surgery were use of IDSM, type of (axillary) surgery and the performance of cavity shaving. Cavity shaves were more often performed when IDSM was used (24% versus 14% in CSR group, p < 0.001), while the proportion of radical first surgeries (93% versus 96% respectively, p = 0.070) was comparable. Conclusion IDSM was associated with a modest reduction in duration of surgery. Surgeons performed more cavity shaves since IDSM but this was not reflected by a lower proportion of patients with positive margins. Table 1. Baseline characteristics of the CSR versus the IDSM cohort Table 2. Results of surgery in the CSR versus the IDSM cohort. Citation Format: Sophie Wooldrik, Elles van de Voort, Taco Klem, Thijs van Dalen, Cornelis Verhoef, Gerson Struik, Erwin Birnie. The effect of intra-operative margin assessment during breast conserving surgery for breast cancer in a Dutch cohort [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO1-23-07.