Abstract PS2-01-05: Improving radical resection rates in patients with breast cancer by intraoperative imaging using bevacizumab-IRDye800CW - the MARGIN-2 study

Abstract Introduction: Tumor-positive margins are reported in 10-11% of patients undergoing breast-conserving surgery (BCS) for breast cancer and require additional therapy (boost radiotherapy or re-excision) to reduce local recurrence risk. Fluorescence imaging (FI) shows promise in reducing tumor-positive margins by intraoperative tumor tissue visualization using tumor-specific tracers. This clinical study aims to identify tumor-positive margins intraoperatively using FI with bevacizumab-IRDye800CW, and assess the feasibility of implementing FI in high-volume breast cancer centers. Methods: Patients with early-stage breast cancer scheduled for BCS were included. Bevacizumab-IRDye800CW was administered intravenously 2-4 days prior to surgery. After the lumpectomy, fluorescence images of both the surgical cavity and resection specimen were obtained. While surgeons proceeded with the sentinel node procedure, the fluorescence images were analyzed and a tumor-to-background (TBR) ratio of higher fluorescence intensity spots were calculated. A TBR 1.5 was considered a risk of a tumor-positive margin and re-excision of the corresponding area was performed in consultation with the surgeon. All fluorescence images were correlated to histopathology results. Results: In total, 53 patients completed all study procedures. Five patients (9.4%) initially had a tumor-positive margin. FI identified all those patients. Re-excision was performed in the same session, resulting in tumor-negative margins in all these cases. In 35 other patients re-excisions were performed because of a high TBR. In hindsight, they had negative margins, but the re-excision was generally performed at the side with the closest margin based on histopathology assessment. Incorporation of FI prolonged the average BCS time by a maximum of five minutes. Conclusion: Targeted-fluorescence guided re-excisions prevented tumor-positive margins in 9.4% of patients undergoing BCS for breast cancer. In our study, no tumor-positive margins were missed and tumors were confirmed to be completely resected. With only a five-minute increase in surgery time, FI seems feasible to implement in a high-volume breast cancer center. Further optimization of tracer specificity and signal depth quantification is needed to improve accuracy and clinical applicability. Citation Format: B. Keizers, J. J. Nijveldt, T. S. Nijboer, H. H. Boersma, F. J. Voskuil, A. H. de Haas, S. Kruijff, P. J. van der Zaag, W. Kelder. Improving radical resection rates in patients with breast cancer by intraoperative imaging using bevacizumab-IRDye800CW - the MARGIN-2 study abstract. In: Proceedings of the San Antonio Breast Cancer Symposium 2025; 2025 Dec 9-12; San Antonio, TX. Philadelphia (PA): AACR; Clin Cancer Res 2026;32(4 Suppl):Abstract nr PS2-01-05.