Ex vivo detection of tumoral lymph nodes of colorectal origin with fluorescence imaging after intraoperative intravenous injection of indocyanine green.

BACKGROUND AND OBJECTIVES

The aim of this study was to investigate the potential role of indocyanine green (ICG) fluorescence imaging after intraoperative intravenous (IV) injection for the "ex vivo" detection of metastatic lymph nodes (mLNs) of colorectal cancer origin.

METHODS

Fresh-fixed LNs in cassettes and/or paraffin-embedded LNs of patients included in a study that evaluated the role of ICG in the detection of peritoneal metastases of colorectal origin (Protocol NCT-01995591) were further explored with a dedicated near-infrared camera system for their fluorescence. An IV injection of ICG was delivered intraoperatively at 0.25 mg/kg. Signal to background ratios (SBRs) were calculated.

RESULTS

LNs on operative specimens were evaluated for 12 patients (5 males, 7 females). A total of 182 LNs were analyzed. The mean LN number per patient was 15.2 (median: 15.5; range 3-22). SBRs of mLNs were significantly more fluorescent than benign LNs, 1.41 versus 1.04 arbitrary units (P < 0.0002). On univariate analysis, fluorescence was statistically correlated with LN surface area (>20 mm(2) ) (P < 0.0004).

CONCLUSION

Ex vivo ICG fluorescence imaging after intraoperative IV injection represents a potential method for detecting invaded LN's of colorectal cancer origin on operative specimens. Further clinical studies are needed to better define optimal techniques. J. Surg. Oncol. 2016;114:348-353. © 2016 Wiley Periodicals, Inc.