Background. The sentinel lymph node (SLN) concept has been proposed to avoid unnecessary invasive LN dissection in surgery for esophageal cancer. This study evaluated a new macrophage-targeting fluorescent agent, indocyanine green-neomannosyl human serum albumin (ICG: MSA), for SLN mapping using a custom-made intraoperative color and fluorescence-merged imaging system (ICFIS) in porcine esophagus.
Methods. The LN targeting ability of ICG: MSA, indocyanine green-human serum albumin (ICG: HSA), and ICG was examined in vitro using the U937 differentiated monocyte cell line and in vivo in a mouse footpad model using fluorescence imaging. SLN identification in rabbit esophagus was then performed using ICG: MSA, ICG: HSA, and ICG. Finally, intraoperative SLN detection was conducted in porcine esophagus after esophagoscopic injection of ICG: MSA.
Results. The fluorescence signal of U937 cells treated by ICG: MSA was significantly higher than that of ICG or ICG: HSA(ICG: 1.0 +/- 0.37; ICG: HSA: 3.4 +/- 0.28, ICG: MSA: 6.8 +/- 1.61; ICG to ICG: HSA, p = 0.03; ICG: HSA to ICG: MSA, p = 0.04; ICG to ICG: MSA, p = 0.0009). ICG: MSA was retained in popliteal LNs as long as 3 h, while ICG rapidly diffused through the entire mouse lymphatic system within 5 min. Esophageal SLN was detected within 15 min after injection of either ICG or ICG: MSA, but ICG: MSA provided more distinguishable images of LNss than ICG in rabbit esophagus. The SLN was also successfully detected in all porcine esophagus; the mean number of SLNs identified per esophagus was 1.6 +/- 0.55.
Conclusions. ICG: MSA has more specific macrophage-targeting properties, which could overcome the limitation of the low SLN retention of ICG, and could provide more precise real-time SLN detection during esophageal cancer surgery.(C) 2016 by The Society of Thoracic Surgeons.