Near-infrared fluorescent imaging with indocyanine green in rabbit and patient specimens of esophageal cancer.

backgroundWe aimed to assess the possibility of detecting esophageal cancer after intravenous injection of indocyanine green (ICG) in preclinical and clinical models.

methodsForty-five rabbits were surgically implanted with VX2 tumors into the esophageal muscular layer 2 weeks before esophagectomy. The rabbits received intravenous injection of ICG at doses of 1, 2, or 5 mg/kg at 3, 6, 12, 24, or 48 h before surgical removal of esophagus. Twelve patients scheduled to undergo esophagectomy were also enrolled, and all received 2 mg/kg of ICG intravenously at 3, 6, 12, or 24 h before surgical removal of esophagus. The fluorescence intensity was measured in all resected specimens from the rabbits and patients using a near-infrared (NIR) fluorescence imaging system after surgery.

resultsEsophageal tumors were successfully established in all rabbits, and fluorescent signals were detected in all animal and patient specimens. Tumor-to-normal ratio (TNR) analysis showed that higher doses resulted in a greater TNR. Injection of at least 2 mg/kg of ICG was required for clear visualization of the tumor, and the TNR was highest at 12 h after injection. The TNR in patients was also highest at 12 h (P=0.0004), with 2 mg/kg of ICG. None of the patients had major complications following ICG injection.

conclusionsNIR fluorescence imaging can be used to visualize esophageal cancer after systemic injection of ICG. ICG at 2 mg/kg at 12 h is optimal for tumor detection. However, since the clinical trials were conducted in a small number of patients, further studies are needed in larger populations.