Frequency and feasibility of detecting FGFR mRNA expression in archival samples of patients with cholangiocarcinoma (CCA).

281Background: Fibroblast growth factor receptor (FGFR) inhibitors show promising activity in patients with intrahepatic CCA harboring FGFR2 fusions, but these alterations have a modest frequency of 15-20%. FGFR mRNA expression has shown preliminary potential as a predictive biomarker for FGFR inhibition in advanced urothelial cancer and is currently being used for patient selection in clinical trials. To assess if we can increase the number of patients with CCA eligible for FGFR inhibitor trials, we evaluated the frequency and feasibility of detecting FGFR mRNA overexpression in archival CCA tissue. Methods: Patients with intrahepatic and extrahepatic CCA who received treatment at the MGH between 1/2004 and 12/2013 were included. Tissue microarrays of archival specimens were stained using the FGFR1-3 pooled, FGFR1, and FGFR2 RNA in situ hybridization probes (RNAscope 2.5 assay). Clinicopathologic data were obtained from the medical record. CCA cell lines were assessed for sensitivity to the FGFR selectiv...