AB149. SOH23ABS_183. Margins in breast cancer: current practice and the implications of wider margins—how much is enough?

Background: Recent data has created confusion with regards to the impact of margin status on reoccurrence and survival among patients undergoing breast-conserving surgery (BCS). The adequacy “no tumour on ink” has been questioned. We aimed to evaluate the effect of compliance with wider margins in patients who underwent BCS within our department.

Methods: A single-centre, retrospective analysis was preformed of patients who underwent BCS from January 2020 to January 2021. A database was constructed from electronic patient records and postoperative histology reports.

Results: A total of 45 patents that underwent BCS were identified. A proportion of 93% had invasive disease and 22% underwent neoadjuvant chemotherapy. The incidence of positive margins was 22% (n=10), defined by “no tumour on ink”. All underwent re-excision of the positive margin. Larger tumour size (29.8 vs. 19.78 mm, P<0.001) and positive sentinel lymph node biopsy (70% vs. 17%) was more common in the re- excised margin group. Lymphovascular invasion (LVI), receptor status and neoadjuvant chemotherapy (NACT) use did not differ between the groups. A proportion of 24% (n=11) would further have required margin excision for extended margin requirements. Five for margins <1 mm from margin for invasive disease and 6 for margins 1–2 mm. A proportion of 29% (n=13) underwent intraoperative cavity excisions with 23% proceeding for further margin re-excision and 1 having a positive margin cleared.

Conclusions: In today’s era of multimodality therapy for breast cancer, margin status is one factor impacting local recurrence risk. If international guidelines should be revised surgeon practice will be required to change to achieve a minimum clear margin of at least 1 mm.

Keywords: Breast; cancer; excision; margins; recurrence