160. Optimising magnetic sentinel lymph node biopsy in an in vivo porcine model

Abstract

The magnetic technique for sentinel lymph node biopsy (SLNB) has been evaluated in several clinical trials, albeit under proscribed conditions. An in vivo porcine model was therefore developed to optimise the magnetic technique by evaluating the effect of differing volume of magnetic tracer and time of injection. A total of 48 sentinel node procedures were undertaken and 423 nodes (109 sentinel nodes) retrieved. There was a significant correlation between magnetometer counts and the tracer content of excised sentinel lymph nodes (SLNs) (r=0.82; p<0.001). Total numbers of tracer-containing SLNs increased with increasing volumes of tracer (p<0.001). Transcutaneous magnetometer counts increased with increasing time from injection of tracer (p<0.0001) and reached a plateau within 60 minutes. A non-statistically significant trend was observed between volume of tracer injected and tracer content of SLNs (p=0.07). We infer that increasing tracer volume and injecting prior to surgery improves transcutaneous 'hotspot' identification, but that very high injection volumes lead to an increase in the number of nodes excised.3