Abstract P1-20-24: Magnetic seed localisation as the new standard of care for nonpalpable breast lesion localisation: A comparison with hooked-wire localisation

Background and aims: Breast cancer is the most frequent type of cancer diagnosed in women. In breast surgery, screening programs and high-resolution imaging result in higher incidence of impalpable breast lesions, requiring preoperative localisation. Several localisation methods have been developed during the past decades. Since September 2018, Magseed® localisation has become standard of care in University Hospitals Leuven, providing an alternative for the widely used hooked-wire localisation method. The aim of this observational study was to compare hooked-wire localisation and Magseed® localisation in terms of oncological safety, clinical safety and surgeon satisfaction. Methods: Data of 100 patients who underwent Magseed® localisation were prospectively collected between September 2018 and April 2019, and retrospectively of 91 patients who underwent hooked-wire localisation between March 2018 and September 2018. Three patients received two Magseeds® resulting in a total of 103 seeds. Similarly, 11 patients received two hooked-wires so 102 wires were included in this study. Results: Baseline patient and tumour characteristics were similar between both groups. All magnetic seeds were placed under ultrasound guidance, with a median of two days in advance, resulting in logistical ease and more patient comfort. Occurrence of haematomas did not significantly differ between Magseed® and hooked-wire placement (2.97% vs 2.13% ; p = 1.000). 96.12% of the magnetic seeds were placed within 5 mm of the target, similar to 98.04% of the hooked-wires (p = 0.683). All seeds were retrieved during surgery, with an unambiguous detection by Sentimag® in 94.06%. The median ratio excised specimen volume to initial breast volume differs significantly between both groups in favour of hooked-wire (4.5% vs 3.7% ; p = 0.049), but the specimen volume itself is almost identical between the two groups. Positive surgical margin rate was lower for Magseed® compared to hooked-wire, although not significant (4.76% vs 10.39% ; p = 0.233). Due to positive margins, one additional mastectomy was performed in the Magseed® group. In contrast, three mastectomies and one additional excision were necessary in the hooked-wire group. 81% of the Magseed® procedures were scored as ‘easier than hooked-wire’ by our surgeons. Conclusion: The positive margin rate and associated re-excision/mastectomy rate was lower with Magseed® localisation compared to hooked-wire localisation. In addition, comparison of the complication rate showed an equal clinical safety profile. Also specimen volumes are similar with both localisation techniques. Moreover, the high surgeon satisfaction and logistical advantages designate Magseed® localisation as preferable over hooked-wire localisation. Citation Format: Amelia Dehaene, Ann Smeets, Hanne Vos, Chantal Van Ongeval, Patrick Neven, Annouschka Laenen, Renate Prevos, Thomas Thywissen, Machteld Keupers, Ines Nevelsteen. Magnetic seed localisation as the new standard of care for nonpalpable breast lesion localisation: A comparison with hooked-wire localisation [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P1-20-24.