Exploratory Study of Superparamagnetic Iron Oxide Dose Optimization in Breast Cancer Sentinel Lymph Node Identification Using a Handheld Magnetic Probe and Iron Quantitation

Abstract

This exploratory study compared doses of ferucarbotran, a superparamagnetic iron oxide nanoparticle, in sentinel lymph nodes (SLNs) and quantified the SLN iron load by dose and localization. Eighteen females aged ≥20 years scheduled for an SLN biopsy with node-negative breast cancer were divided into two equal groups and administered either 1 mL or 0.5 mL ferucarbotran. Iron content was evaluated with a handheld magnetometer and quantification device. The average iron content was 42.8 µg (range, 1.3-95.0; 0.15% of the injected dose) and 21.9 µg (1.1-71.0; 0.16%) in the 1-mL and 0.5-mL groups, respectively (p = 0.131). The iron content of the closest SLN compared to the second SLN was 53.0 vs. 10.0 µg (19% of the injected dose) and 34.8 vs. 4.1 µg (11.1%) for the 1-mL and 0.5-mL groups, respectively (p = 0.001 for both). The magnetic field was high in both groups (average 7.30 µT and 6.00 µT in the 1-mL and 0.5-mL groups, respectively) but was not statistically significant (p = 0.918). The magnetic field and iron content were correlated (overall SLNs, p = 0.02; 1-mL, p = 0.014; 0.5-mL, p = 0.010). A 0.5-mL dose was sufficient for SLN identification. Primary and secondary SLNs could be differentiated based on iron content. Handheld magnetometers could be used to assess the SLN iron content.

Keywords: RI; SLN; SLNB; SPIO; breast cancer; iron quantitation; magnetic probe; optimal dose.

Figure 1

Comparison of iron content in the closest sentinel lymph node (SLN) to the tumor, according to injection volume. Biopsied SLNs had their magnetic field quantified using a magnetometer and their iron content quantified using the iron quantification device described in Kuwahata et al. [11]. (a). Boxplot of iron content of SLNs according to the volume of ferucarbotran injected. Pearson’s test was used to compare patients who received 1.0 mL of ferucarbotran (average iron content 42.8 μg) vs. 0.5 mL (average iron content 21.9 μg) (p = 0.131). (b–d) Correlation of magnetic fields recorded using the magnetometer vs. the iron content measured using the iron quantification device. (b) Total participants and the correlation coefficient 0.57; p = 0.02. (c) Participants who received 1.0 mL of ferucarbotran and the correlation coefficient 0.59; p = 0.014. (d) Participants who received 0.5 mL of ferucarbotran and the correlation coefficient 0.63; p = 0.0102.