Peri-hilar cholangiocarcinoma (phCCA): A comparative comprehensive genomic profiling study.

Abstract

542 Background: CCA is a heterogenous group of malignancies that arise from epithelium of the biliary tree. The comparison of the genomic landscapes that can influence therapy selection of phCCA from other types of intra- and extra-hepatic CCA (ih/ehCCA) are not well-known. We queried differences in comprehensive genomic profiles (CGP) of CCAs and comparing genomic alterations (GA) in phCCA and other types of CCA. Methods: DNA extracted from 110 cases of phCCA, 743 cases of common bile duct CCA (cbdCCA) and 9178 cases of intrihCCA underwent hybrid capture-based CGP to evaluate GA, MSI status, TMB levels, genomic ancestry, genomic signature, HRD score and germline status. phCCA cases were confirmed at surgery and pathology as originating from either the left, right or common hepatic ducts. cbdCCA cases were confirmed either by CBD biopsies or Whipple procedures. PD-L1 expression was determined by IHC using the Dako 22C3 assay using the tumor proportional score (TPS) system. Results: Patient characteristics were similar (Table). The GA/tumor and frequencies of European ancestry were similar. Both phCCA and cbdCCA featured significantly greater frequency of ERBB2 GA than ihCCA (P=.002) and lower frequencies of FGFR2 GA (P=.001) and IDH1 GA (P=.006). ihCCA featured significantly higher frequencies of FGFR2 (11.7%) and IDH1 (13.9%; P=.006) GA than either phCCA or cbdCCA. cbdCCA had a significantly higher frequency of KRAS GA than phCCA (P=.015) and ihCCA (P<.001). The KRAS G12C frequency reached 5.9% of KRAS mutated ihCCA. GA in BRAF, PIK3CA, CDKN2A and MTAP were not significantly different. TP53 GA were higher in cbdCCA than phCCA (P=0.011) and combined phCCA and cbdCCA (ehCCA) were higher than ihCCA (P=.071). MSI status, TMB levels and PD-L1 expression was similarly low in all 3 groups. Positive homologous recombination deficiency (HRD) scores based on %gLOH and high frequencies of MMR genomic signatures were similar in all 3 groups. Conclusions: phCCA appears to be a distinctive form of ehCCA featuring significantly higher frequencies of potentially targetable ERBB2 and lower frequencies of targetable FGFR2 and IDH1 mutations, when compared to ihCCA. Predictive IO markers were similarly low in both ihCCA and ehCCA.[Table: see text]