Correspondence to: Fredrik Wärnberg (e-mail: fredrik.warnberg@vgregion.se)
Department of Surgery
Sahlgrenska University Hospital
Gothenburg S-413 45
Sweden
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BJS, https://doi.org/10.1093/bjs/znaf129, published 23 July 2025
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Dear Editor
We thank Dr Zhang and Dr Zhu for their interest in our study1 and for their comments. Skin staining might be an even smaller problem in women with darker skin. However, we were not able to study this as almost all our patients were white Caucasians.
Regarding safety, we used a 10 to 20 times lower dose than the 1-2 ml injection routinely used and recommended by the producer of Magtrace. The larger doses have been usen in thousands of patients without serious toxicity and earlier, nanoparticles of iron oxide have been used as an intravenous contrast for magnetic resonance tomography. Given that this is a dose-de-escalation study of a tracer, the safety2 of which has been cleared by major regulatory bodies, safety of a smaller dose was not a concern.
Finally, we presented the sentinel lymph node (SLN) detection ratios for Magtrace® (Endomagnetics Ltd, Cambridge, UK) and technetium per hospital. The study was not designed to test non-inferiority per hospital, but SLN detection was 4% lower or less at all sites. However, we did not formally compare hospitals, and we chose not to draw any conclusions from per hospital data.
References
Sundh L, Alzoubi M, Abu-Oddos N, Båtelsson S, Nyman P, Karakatsanis A et al. Ultra-low dose superparamagnetic iron oxide nanoparticle injection for sentinel lymph node detection in breast cancer: prospective cohort study. BJS 2025. doi: 10.1093/bjs/znaf129
Wang AZ, Gu FZ, FarokhzadOC. Nanoparticles for Cancer Diagnosis and Therapy. In: Webster, T. (eds) Safety of Nanoparticles. Nanostructure Science and Technology. 2009. Springer, New York, NY. doi: https://doi.org/10.1007/978-0-387-78608-7_10.
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