Su1759 Ex-Vivo Characterization of Liver and Peritoneal Metastases by Confocal Laser Endomicroscopy: The PERSEE Project

Abstract

Rationale: In digestive oncology, the rapid evaluation of the local and regional extent of cancer is crucial to determine the best therapeutic treatment for the patient. Indeed, the presence of metastases can significantly worsen the prognosis and change drastically the choice of therapy. For this reason, a minimally invasive surgical exploration that evaluates the local and metastatic extent of cancer is generally required before the tumor resection. Probe-based Confocal Laser Endomicroscopy (pCLE) is a new promising imaging technique enabling microscopic analysis of tissues, at cell resolution, in real time. Objective: First evaluation of pCLE for the discrimination of benign or metastatic nodules in liver and peritoneum.Methods: Several fresh samples of liver and peritoneal nodules were analyzed ex vivo right after the resection using a endomicroscopy system and a UHD confocal miniprobe. Healthy samples of the same tissues were also analyzed for comparison. Indocyanine green (ICG) was topically applied on the specimens (2.5mg/ml). For each sample, side by side comparison with histology was performed. Results. We analyzed and correctly identified metastatic (n=5) and inflammatory (n=4) peritoneal nodules, and metastatic liver nodules before (n=6) and after (n=2) treatment with chemotherapy. In healthy peritoneal CLE images (aquired on 10 samples) the adipocytes, surrounded by the extra-cellular matrix (ECM) composed by a strongly and uniformly fluorescent connective tissue, were clearly recognizable. In healthy liver CLE images (acquired on 7 samples), a compact line-structure of hepatocytes was observed. Following features could also be seen in both liver and peritoneal cancerous nodules: the irregular associations of cells forming tubular structures typically found on adenocarcinoma histology; the strongly inhomogeneity in the fluorescence signal of the ECM compared to healthy tissue. In contrast to the adenocarcinoma, the connective tissue composing the ECM of inflammatory peritoneal nodules seemed to be more abundant than in the healthy tissues and with a uniform fluorescent signal. Lastly, after chemotherapy treatment, the liver metastatic nodule appeared to have a very compact and fluorescent fibrotic tissue that replaces the tubular cell structures typical of the adenocarcinoma. Conclusion: Our preliminary results suggest that pCLE is a promising tool for an immediate identification of metastases both in liver and peritoneal tissues. This study reveals that the structure of the ECM may be an important additional parameter to take into account in order to improve diagnosis. In vivo use of this innovative approach should enable us to directly detect cancer without the need of more invasive and time-demanding biological sampling.