Abstract P3-03-12: SentiDose interim analysis. A dose optimizing study with a super paramagnetic iron oxide for sentinel node detection

Background Superparamagnetic iron oxide nanoparticles (SPIO) is a novel tracer for axillary mapping in breast cancer with comparable performance to the dual standard of isotope and blue dye. The earlier SPIO (Sienna+ ® ) required 2 ml of SPIO diluted in 3 ml NaCl and was injected retro-areolarly. This was considered to be associated with the discoloration observed in 40% of breast conservation cases. Subsequently, a new form was developed (SiennaXP TM ) in a volume of 2 ml without dilution. The aim of the ongoing SentiDose study is to compare smaller doses of SiennaXP TM injected in different time-frames (1.5 ml periareolarly on the operation day vs 1 ml peritumourally 1-7 days preoperatively) and compare it to the performance of the original SPIO (Sienna+ ® ). A background mapping with isotope and blue dye was performed for assessment of concordance. Method In all, 330 patients will be recruited from six sites in Sweden, divided in two isonumerical cohorts injected as described above. Results from the 1.5 ml cohort are presented and compared on a patient-level analysis to the SentiMag Nordic trial that used Sienna+ ® , on a 2-sided non-inferiority margin of 5%. Study endpoints are detection rate per patient, number of sentinel nodes (SN) retrieved and discoloration at 3 weeks postoperatively. Results Detection rate for SiennaXP TM , 1.5 ml, was comparable with Sienna+ ® (96.9 vs 97.6%, p=0.76), even in multivariate analysis adjusting for age and metastasis rate (Exp(B)=0.68; 95% CI; 0.18-2.60, p=0.58). with a high concordance between isotope and SiennaXP TM . The number of SNs were similar (1.91 vs. 1.83, p=0.08) for Sienna+ ® and SiennaXP TM . Discoloration rate was lower for SiennaXP TM compared to Sienna+ ® (14.3% vs. 38.2%, p Demographics and outcomes are illustrated in Conclusion The periareolar injection of 1.5 ml SiennaXP TM on the day of the operation provides comparable detection rates with much less skin discoloration, providing effectivity and flexibility. The completion of the SentiDose study will allow for more definitive results on the dose, timeframe and injection site of SPIO. Citation Format: Hersi A-F, Obondo C, Pistioli L, Abdsaleh S, Nilsson F, Mohammed I, Eriksson S, Warnberg F, Karakatsanis A. SentiDose interim analysis. A dose optimizing study with a super paramagnetic iron oxide for sentinel node detection [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P3-03-12.