Magseed placement before neoadjuvant chemotherapy to facilitate subsequent breast- conserving surgery - a single-centre audit

Background: A radio-opaque clip is placed in all patients planned for breast-conserving surgery (BCS) receiving neoadjuvant chemotherapy (NACT) to localise the tumour bed in case response to chemotherapy makes later localisation impossible. A tumour that was localised with a radio-opaque clip before NACT will then need a second localisation procedure, after the completion of NACT to aid BCS. The two most commonly used methods are hookwire and radio-guided occult lesion localisation. Magseed (R), a newly available technology consisting of a small magnetic seed, has now become available. The seed is placed instead of a radio-opaque clip before the start of or during NACT and can remain in place until the time of BCS. Methods: A retrospective cohort study was performed, collecting data on patients who had a Magseed placed before or during NACT from December 2018 to February 2020. Results: Twenty-one Magseed devices were placed into the breasts of 20 patients, 18 under ultrasound guidance, and three under stereotactic guidance. The average breast volume of individuals who had seeds placed was 1 532 g +/- 869 g. The duration that the seeds were in situ was 138 days +/- 45 days. All preoperatively placed seeds were retrieved at the surgery with no observed migration outside the tumour bed. Conclusion: Magseed placement before NACT is a safe and technically simple technique that can be done under ultrasound guidance in the majority of cases. It has the advantage of being a single procedure with an associated reduction in time off work and travel cost to the patient, as well as flexibility in terms of the time of placement.