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 (SiennaXPTM) in a volume of 2 ml without dilution. The aim of the ongoing SentiDose study is to compare smaller doses of SiennaXPTM 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 SiennaXPTM, 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 SiennaXPTM. The number of SNs were similar (1.91 vs. 1.83, p=0.08) for Sienna+® and SiennaXPTM. Discoloration rate was lower for SiennaXPTM compared to Sienna+® (14.3% vs. 38.2%, p<0.001) after breast conserving surgery. Furthermore, two patients were excluded in the SentiDose cohort due to protocol violation.

Demographics and outcomes are illustrated in

Table 1 Nordic SentiMag Trial (n=206)SentiDose 1.5ml Cohort (n=163)p-valueAge (yrs)61.864.30.03BMI (kg/m2)26.927.20.84Size (mm)19.220.00.64Type of Surgery (BCS/Mx)154 (74.8%) / 52 (25.2%)130 (79.8%) / 33 (20.2%)0.26SPIO Detection Rate (per patient)97.6%96.9%0.76SPIO-Tc Concordance97.5%97.5%0.42Mean SPIO detected SN1,831,910.08Metastasis Rate26.2%16.0%0.01SPIO nodal rate in malignancy91.2%81.6%0.21Discoloration in BCS38.2%14.3%<0.001

Conclusion

The periareolar injection of 1.5 ml SiennaXPTM 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, Wärnberg 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.