761 Distinguishing Benign From Malignant Dominant Biliary Strictures in Patients With Primary Sclerosing Cholangitis Utilizing Probe-Based Confocal LASER Endomicroscopy (pCLE): a Multi-Center, Expert Consensus Review

Background: Primary Sclerosing Cholangitis (PSC) patients are at high risk for cholangiocarcinoma. Distinguishing benign from malignant dominant biliary strictures by cholangiography and cytology is challenging. Probe-based confocal laser endomicroscopy (pCLE) enables subepithelial visualization of biliary strictures during ERCP. A multi-center, prospective registry study of 102 patients with indeterminate biliary strictures (Meining, GIE 2011) revealed very high sensitivity (98%) and NPV (97%). Limited data utilizing pCLE in PSC patients exists. Whether the intense periductular fibrosis and inflammation may alter pCLE interpretation or if expert consensus can be achieved on characterization of findings in this patient population remains unknown. Aim(s): Evaluate the performance characteristics of pCLE to distinguish between benign and malignant dominant PSC stenosis by blinded consensus review of image sequences. Method(s): 10 pCLE experts from 9 centers (8 US, 1 EU) met at a consensus meeting to evaluate pCLE findings in patients with PSC strictures. Recorded pCLE video sequences acquired during ERCP using the CholangioFlexTM confocal mini probe (Mauna Kea Tech. Paris, France) passed through a cholangioscope or catheter were reviewed. Investigators were blinded from clinical information and, in addition to the normal and malignant Miami criteria, utilized newly recognized inflammatory criteria that include "scales", thickened reticular pattern, and increased intra-glandular space (GIE 75(4S)2012:AB381). Patients with a minimum two of five malignant Miami criteria were classified as "suspicious", one as "reactive"; a normal reticular pattern was "benign". Tissue sampling results at time of ERCP was considered positive if malignant cytohistopathology. ROC curve analysis for pCLE performed. Result(s): pCLE sequences from 46 dominant PSC strictures were pooled from five centers. A presumptive diagnosis based on tissue sampling results and clinical follow-up was benign (n=39) and malignant (n=7). Combining pCLE and tissue sampling yielded sensitivity and NPV of 100%. See Table for detailed operating characteristics. See Figure for ROC of pCLE. AUC = .82 (CI .68-.92; p < .001). Conclusion(s): The operating characteristics of tissue sampling in our PSC patient cohort were higher than historical controls and likely related to selection bias of the sequences reviewed. The combination of pCLE and tissue sampling in the evaluation of dominant PSC strictures has a high ability to exclude malignancy and may be helpful in determining surveillance intervals in this high-risk population. Operating characteristics of pCLE in the setting of PSC should further improve with increased experience of recognizing inflammatory criteria. A multicenter, international registry of pCLE in PSC patients is ongoing. (Figure Presented).