Abstract P2-01-11: SentimagIC: A non-inferiority trial comparing super paramagnetic iron oxide vs. Tc99 and blue dye in the detection of axillary sentinel nodes in patients with early stage breast cancer

Background: Sentinel lymph node biopsy (SLNB), performed using radioisotope tracer with or without blue dye, is a highly accurate method for staging the axilla in early breast cancer. A radioisotope tracer with or without blue dye is the most commonly used technique for SLNB. Superparamagnetic iron oxide mapping agents detected by a handheld magnetic probe have been explored to overcome the disadvantages of the standard technique which include the short half-life, availability, handling and disposal issues for radioisotope, and the risk of allergic reactions to blue dye. Iron oxide mapping agents have been shown to be non-inferior to the standard technique in European studies. The SentimagIC trial was designed to establish the non-inferiority of a new formulation of the magnetic tracer, SiennaXP, to the combination of radioisotope and blue dye and was required to support a US regulatory submission.

Methods: Between January and December 2015, 160 patients with clinically node negative early stage breast cancer were recruited from six centers in the United States. Subjects received radioisotope injection then an intraoperative subareolar injection of SiennaXP and isosulfan blue dye prior to SLNB being performed. The sentinel node identification rate was compared between SiennaXP and the standard technique to evaluate concordance and non-inferiority.

Results: 147 procedures were completed in 147 subjects. A total of 369 histologically confirmed nodes were excised. The nodal detection rate was 94.3% (348/369) with SiennaXP and 93.5% (345/369) with the standard technique (difference 0.8%, 95% binomial confidence interval lower bound -2.1%). The per-subject detection rate was 99.3% (145/146) with SiennaXP and 98.6% (144/146) with the standard technique (one subject excluded due to not contributing any analyzable nodes). There were 22 subjects with positive SLNs, of whom 21 (95.4%) were detected by both SiennaXP and the standard tracers. In one subject, a positive node was not identified by any tracer, but was removed as clinically suspicious. The number of nodes excised per subject was 2.4 for both SiennaXP and for the standard combined technique.

Conclusion: This study showed SiennaXP is non-inferior to the standard dual technique of radioisotope and blue dye for axillary sentinel lymph node detection in early stage breast cancer and this provides a potential alternative to radioisotope and blue dye.

Citation Format: Alvarado M, Bold R, Gittleman M, Beitsch P, Blair S, Harmer Q, Kivilaid K, Teshome M, Thompson A, Mittendorf E, Hunt K. SentimagIC: A non-inferiority trial comparing super paramagnetic iron oxide vs. Tc99 and blue dye in the detection of axillary sentinel nodes in patients with early stage breast cancer [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P2-01-11.

Abstract OT2-02-03: Magnetic nano-device for identification of the breast sentinel nodes – A novel method

Breast sentinel node biopsy (SNB) is a well-established procedure that has supplanted traditional axillary dissection for most clinically node-negative breast cancer patients. Techniques to identify the draining lymph nodes include colored dyes and radioactive compounds. The Sentimag system uses a non-radioactive magnetic tracer and a handheld magnetic probe to identify sentinel nodes (SNs). The Sentimag Intraoperative Comparison (SentimagIC) study compares the magnetic technique with the standard combination of radioisotope and isosulfan blue dye.

Methods: SiennaXP is a nano device composed of coated iron oxide nanoparticles designed to optimize lymphatic uptake and SN retention. The Sentimag breast SNB technique involves injection of 2cc of SiennaXP fluid into Sappey's subareolar plexus followed by 5 minutes of breast massage and an additional 15 minutes of time to optimize drainage prior to beginning the procedure. The Sentimag hand held probe is then used to identify a magnetic 'hotspot' through the skin of the axilla. The usual transverse axillary incision is made and the magnetometer is used to identify the SNs. The SentimagIC study involves utilizing the Sentimag technique in combination with the 'standard' techniques of isosulfan blue dye and 99technetium sulfur colloid. All blue, radioactive and magnetic SNs are removed and identified as stained blue (from isosulfan blue dye) or black/brown (from SiennaXP) or not, and both radioactive and magnetic counts are taken ex vivo on each node. Currently there are 6 active sites with a total of 60 patients enrolled.

Trial design: This is a pivotal, prospective, open label, multicenter, paired comparison of the magnetic technique with the standard of care for lymph node localization in patients with breast cancer.

Primary endpoints: The lymph node detection rate with SentiMag / SiennaXP and the detection rate with the standard of care; and the safety of Sentimag / SiennaXP as indicated by adverse events.

Eligibility: Diagnosis of primary breast cancer or pure ductal carcinoma in situ (DCIS); Scheduled for sentinel lymph node biopsy; Clinical negative node status (i.e. T0-3, N0, M0).

Statistical methods: The primary hypothesis is that the magnetic technique is non-inferior to the standard technique. Based on an expected detection rate of 95% for both techniques and a non-inferiority margin of 5%, 140 subjects will be required to show non-inferiority with 85% power.

Discussion: SNB for breast cancer is a robust procedure, able to identify the draining lymph nodes of the breast in essentially all patients. Many techniques have been used including radioactive tracers (utilized on most cases) and colored dyes. SentiMag utilizes a unique nano device that can identify the same draining nodes but without the radioactivity used in most procedures. Radioactive dyes must be handled carefully to minimize radiation exposure to healthcare providers and the patient from the manufacturing process, delivery to facility, injection under a nuclear physician license, and the surgical procedure. This novel technique may supplant radioactive tracers allowing SNs to be removed without the patient/healthcare providers being exposed to radiation or the scheduling inconvenience of pre-procedure injection.

Citation Format: Beitsch PD, Hunt KK, Bold RJ, Gittleman MA, Blair SL, Alvarado MD, Harmer QJ. Magnetic nano-device for identification of the breast sentinel nodes – A novel method. [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 OT2-02-03.