Abstract P1-01-27: SentiMAG multicentre trial*: Comparison of sentinel node biopsy identification rates using a magnetic tracer vs. standard technique. * UKCRN ID 12178 (UK); NTR 3283 (Netherlands)
Authors: Douek M , Monypenny I , Klaase J , Kothari A , Zechmeister K , Brown D , Drew P , Wyld L , Garmo H , Castro F , Anninga B , Pankhurst Q , ten Haken B , Hall-Craggs MA , Pinder S , Purushotham A 
Published: August 2014

Background: The SentiMAG Multicentre Trial, an international phase II paired equivalence trial, evaluated a new magnetic technique for sentinel node biopsy (SLNB) against the standard (radioisotope and patent blue dye; or radioisotope alone). The magnetic technique does not utilize radiation and provides both a colour change (brown dye) and a hand-held probe for node localization. The primary end-point of this trial was defined as the proportion of sentinel nodes detected with each technique (identification rate) and was found to be non-inferior with the magnetic when compared to the standard technique, in the primary analysis on 160 patients (95% vs 94%, 0.62% difference; 95% upper confidence limit 4.4%). The trial was extended to 350 patients in order to evaluate identification rates further with each technique and at each trial site.

Methods: Women with breast cancer scheduled for SLNB, who were clinically and radiologically node negative, were recruited from 7 centres in the UK and the Netherlands. Sentinel node biopsy was undertaken after administration of both the magnetic and standard tracers (radioisotope +/- blue dye). To determine local identification rate with both techniques, a minimum of 30 cases were recruited at each site.

Results: A total of 364 patients were recruited and 17 were excluded due to a breech of protocol (e.g: no radioisotope or magnetic dye given). SLNB procedures were undertaken on 347 patients. The overall identification rate was 96.3% (334/347) with the standard technique and 91.9% (319/347) with the magnetic technique (4.3% difference; 95% upper confidence limit 7.2%; 9.5% discordance). The identification rate was 93.4% (324/347) with the radioisotope alone (compared with magnetic technique 1.4% difference; 95% upper confidence limit 4.5%; 11.2% discordance). Identification rates with the standard technique at each site, ranged between 87% - 100% and with the magnetic technique between 84% - 100%. Of the 21% (72/347) of patients with lymph node involvement, 15% (51/347) had at least 1 macrometastasis and 6% (21/347), a micrometastasis only. Another 2% (8/347) had isolated tumour cells. Of 825 lymph nodes removed, 625 (76%) were true sentinel nodes identified with the standard technique. The lymph node retrieval rate was 2.38 nodes per patient overall, 1.80 nodes per patient with the standard technique and 1.83 nodes per patient with the magnetic technique.

Conclusion: The magnetic technique is a feasible technique for SLNB, with an identification rate non-inferior to the radioisotope technique but inferior to the standard technique, within the non-inferiority margins setout for this trial. Variation exists in sentinel node identification rates between sites with both techniques.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P1-01-27.