Timing of indocyanine green injection prior to laparoscopic colorectal surgery for tumor localization: a prospective case series.

BACKGROUND: Accurate identification of tumor sites during laparoscopic colorectal surgery helps to optimize oncological clearance. We aimed to assess the timing of the local injection preoperatively and clarify the usefulness and limitation of tumor site marking using indocyanine green (ICG) fluorescence imaging. METHODS: Consecutive patients who underwent primary colorectal cancer surgery from September 2017 to January 2019 were included. Preoperatively, lower endoscopy was used to inject the ICG solution into the submucosal layer near the tumor. During laparoscopic surgery, ICG fluorescence marking as the tumor site marking was detected using a laparoscopic near-infrared camera system. The detection rate and factors associated with successful intraoperative ICG fluorescence visualization including the interval between local injection and surgery were evaluated. RESULTS: One hundred sixty-five patients were enrolled. Using the laparoscopic near-infrared system, the intraoperative detection rates of ICG marking were 100% for ICG injection within 6 days preoperatively, 60% for injection between 7 and 9 days preoperatively, and 0% for injection earlier than 10 days preoperatively. There were no complications associated with ICG marking. Additionally, this method did not disturb the progress of the surgical procedure because injected ICG in the submucosal layer did not cause any tissue inflammation, and if ICG spilled into the serosa, it was invisible by white light. CONCLUSION: Advantages of ICG fluorescence tumor site marking were high visibility of infrared imaging during laparoscopic colorectal surgery and minimal adverse events of surgery. One of the most important findings regarding practical use was a rapid decrease in fluorescence marking visibility if one week passed from the time of ICG local injection.

Intraoperative Identification of Colonic Tumor Sites Using a Near-Infrared Fluorescence Endoscopic Imaging System and Indocyanine Green.

BACKGROUND: This study aimed to investigate the feasibility of the PINPOINT® Endoscopic Fluorescence Imaging System (PINPOINT) for intraoperative identification of colonic tumor sites during laparoscopic colorectal surgery. METHODS: Eighty consecutive patients with colorectal cancer were prospectively enrolled. Preoperatively, 0.5 mL of indocyanine green (ICG; 2.5 mg/mL) was injected into the submucosal space only at the distal side of the tumor under colonoscopy. Intraoperatively, we identified the tumor site on a PINPOINT image in which near-infrared fluorescence was superimposed in pseudocolor on a white light image. We estimated the intraoperative visibility rate of the tumor site and safety of ICG injection and assessed the interobserver variability of visibility grade between 2 surgeons. RESULTS: The intraoperative visibility rate of the tumor site was 93.8% (75/80). The visibility rate at an interval between injection and surgery of <7 days was significantly better than that at an interval of ≥10 days (p < 0.001). The kappa value between 2 observers was 0.827 (95% CI 0.635-1.019) with an agreement rate of 92.5%. There were no preoperative adverse reactions to ICG or intraoperative complications. CONCLUSIONS: Using ICG with the PINPOINT for identifying colonic tumor sites was feasible without any adverse effects during laparoscopic colorectal surgery.