Real-time surgical margin assessment using ICG-fluorescence during laparoscopic and robot-assisted resections of colorectal liver metastases

Almost a third of the resections in patients with colorectal liver metastases (CRLM) undergoing curative surgery, end up being tumor-margin positive (≤1 mm margin). Near-infrared fluorescent (NIRF) imaging using the fluorescent contrast agent indocyanine green (ICG) has been studied for many different applications. When administered in a relatively low dose (10 mg) 24 hours prior to surgery, ICG accumulated in hepatocytes surrounding the CRLM. This results in the formation of a characteristic fluorescent 'rim' surrounding CRLM when located at the periphery of the liver. By resecting the metastasis with the entire surrounding fluorescent rim, in real-time guided by NIRF imaging, the surgeon can effectively acquire margin-negative (>1 mm) resections. This pilot study aims to describe the surgical technique for using near-infrared fluorescence imaging to assess tumor-margins in patients with CRLM undergoing laparoscopic or robot-assisted resections. Out of our institutional database we selected 16 CRLM based on margin-status (R0; n=8, R1; n=8), which were resected by a minimally-invasive approach using ICG-fluorescence. NIRF images acquired during surgery, from both the resection specimen and the wound bed, were analysed for fluorescent signal. We hypothesized that a protruding fluorescent rim at the parenchymal side of the resection specimen could indicate a too close proximity to the tumor and could be predictive for a tumor-positive surgical margin. NIRF images were correlated to final histopathological assessment of the resection margin. All lesions with a NIRF positive resection plane were reported as having a tumor-positive margin. Lesions that showcased no protruding rim in the wound bed were diagnosed as having a tumor-negative margin in 88% of cases. A 5-step surgical workflow is described to document the NIRF signal was used assess the resection margin for future clinical studies. The pilot study shows that image-guided surgery using real-time ICG-fluorescence has the potential to aid surgeons in achieving a tumor-negative margin in minimally invasive liver metastasectomies. The national multi-centre MIMIC-Trial will prospectively study the effect of this technique on surgical tumor-margins (Dutch Trial Register number NL7674).