71288 - Sentinel lymph node detection with an ultra-low dose of superparamagnetic iron oxide nanoparticles in patients with breast cancer

Abstract Introduction Sentinel lymph node (SLN) detection in patients with breast cancer using 1-2 mL superparamagnetic iron oxide nanoparticles (SPIO) has shown comparable results to Technetium99m (Tc99m)+/-blue dye (BD). In a pilot study, we have shown that an ultra-low dose (0.1 mL) SPIO injected intradermally was feasible. This current study, MagSnow 2.0, aims to validate the ultra-low intradermal SPIO dose in a larger cohort. Preliminary data are presented. Method A total of 220 patients scheduled for SLN biopsy will be prospectively enrolled at five Swedish hospitals in this non-inferiority study. All patients receive an intradermal injection of 0.1 mL SPIO up to 30 days before surgery and Tc99m+/-BD according to clinical routine. Primary endpoint is SLN detection. Chi-square test was used to compare proportions and T-test for comparing number of SLNs. Result In this interim analysis including 124 patients, with median age of 63 years, BMI 25.1 kg/m2, tumor size 15 mm and predominantly invasive ductal cancers (80.2%), underwent breast conserving surgery (96.0%) or mastectomy. SLN detection with SPIO was 97.6% and with Tc99m+/-BD 98.4% (p=0.65). The mean number of SLNs detected with SPIO was 1.66 (median 1, IQR 1-2) and Tc99m+/-BD 1.72 (median 2, IQR 1-2) (p=0.60). Discussion These findings support the non-inferiority of an intradermal ultra-low dose of SPIO compared to Tc99m+/-BD for SLN detection. SPIO can be injected weeks before surgery and no nuclear medicine facilities are needed. Skin discoloration and magnetic resonance imaging artefacts are currently investigated in 50 patients from the pilot study.