Dose Comparison (1 mL versus 2 mL) of Superparamagnetic Tracer for Sentinel Node Biopsy in Early Breast Cancer:...

Superparamagnetic iron oxide (SPIO) tracers offer a radiation-free technique for sentinel lymph node biopsy (SNB) in early breast cancer (eBC). However, the data on optimal administration in daily practice, such as the optimal tracer volume and injection method, are still lacking.

In this real-world data analysis, patients with clinically node-negative eBC who underwent SNB with SPIO (Magtrace®) between January 2020 and December 2022 were included. Primary endpoint was the impact of tracer volume on the detection rate. Secondary endpoints evaluated number of removed sentinel lymph nodes, surgical time, and the impact of tracer timing and body mass index (BMI) on detection rate.

A total of 456 patients were included in the study. Overall, 223 patients received 1 mL and 232 patients 2 mL of SPIO. The median time of tracer application was 4 days. Detection rates were similar between both groups (95.5% for 1 mL vs. 96.1% for 2 mL; p = 0.707), with a median of 2.0 sentinel nodes removed in both groups (p = 0.205). The median time of surgery was 70 min in the 1 mL group and 72 min in the 2 mL group, p = 0.972. The detection rate was 97.3% and 95.3% when tracer was injected before and after the median time of application, respectively (p = 0.286). BMI of ≥25 kg/m² led to a detection rate of 94.9% in the 1 mL group and 94.2% in the 2 mL group (p = 0.520).

In this large real-world analysis, 1 mL and 2 mL were similar in the clinical performance of SNB in eBC. High detection efficacy was found regardless of tracer timing and BMI. This real-world analysis reinforces SPIO's role as an effective and adaptable alternative to conventional tracers in SNB for eBC.