Abstract P3-01-04: Improved sentinel lymph node detection with the use of superparamagnetic iron oxide tracer after neoadjuvant treatment in breast cancer patients
Authors: Rubio IT , Esgueva-Colmenarejo A , Diaz-Botero S , Peg V , Espinosa-Bravo M 
Published: May 2016

Abstract
Background. The use of superparamagnetic iron oxide (SPIO) tracer for sentinel node biopsy (SLN) has shown non inferiority compared with the radioisotope technique in early breast cancer. In the neoadjuvant setting (NAC) identification rates with dual technique (blue dye and Tc 99) have been reported to be from 80% to 95%. SLN biopsy false negative (FN) rates after NAC have decreased with the use of dual tracer (radioisotope/ blue dye) and the excision of &gt; 2 SLNs. This study was designed to evaluate the outcome of SLN after NAC using a dual tracer (SPIO and Tc99) versus SLN after NAC with radioisotope (Tc 99) alone.
Material and Methods. After NAC, 188 patients underwent SLN with Tc99 (group Tc99) and 92 patients underwent a SLN with dual technique (group SPIO/Tc99). Inclusion criteria were patients T1-3 N0-1 before NAC and all patients had clinically and /or ultrasound negative axilla before the SLN procedure. Patients were injected subareolar with Tc99 the day before surgery and with the SPIO intraoperatively. SLN was excised if it was radioactive, magnetic or palpable. Patients signed an inform consent. Patients who were N0 pre and postNAC did not undergo an axillary lymph node dissection (ALND) (except for the initial validation patients) , while patients who were N1 pre NAC and N0 post NAC underwent SLN and ALND as part of the protocol.
Results. Mean age of patients between groups were similar, 53.18 (range, 24-90 years old) in the Tc99 group and 52.53 (range, 23-82 years old) in the SPIO/Tc99. Identification rates were 95.72% and 97.8 % in the Tc99 and the SPIO/Tc99 group respectively (p = 0.21). In the Tc99 group, 58 (30.8%) patients were cN1 pre NAC while 13 (14%) in the SPIO/Tc99 (p =0.01). Rates of positive SLN after NAC were 32% in the Tc99 group while 20% in the SPIO/Tc99 group. False negative rates were 4.19% in the Tc99 group (1/50) and 8.3% in the SPIO/Tc99 group (1/13) (p=0.62). There was a statistically significant difference in the median number of SLNs between techniques, being 2.04 in the Tc99 and 2.60 in the SPIO/Tc99 group (p = 0.001). When the mean number of SLNs and the identification rates were differentiated between cN1 and cN0, the statistically significant differences remained unchanged.
Conclusions. The use of dual technique (SPIO and Tc99) for the detection of SLN after NAC increases the identification rates over 97%, better than the reported studies in the NAC setting with Tc99 and blue dye. Although in our study increasing the number of SLNs excised has not decreased the false negative rates, rates of FN are below 10% in both groups. Larger number of cN1 patients is needed in the SPIO/Tc99 technique to validate these initial results. The dual technique with SPIO and Tc99 may optimize the success of SLN after NAC in breast cancer patients.
Citation Format: Rubio IT, Esgueva-Colmenarejo A, Diaz-Botero S, Peg V, Espinosa-Bravo M. Improved sentinel lymph node detection with the use of superparamagnetic iron oxide tracer after neoadjuvant treatment in breast cancer patients. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P3-01-04.