Abdel‐Wahab, Reham

PURPOSE Intrahepatic cholangiocarcinoma (IHCCA), a global health problem, is increasing in incidence and has differing etiologies worldwide. Next-generation sequencing (NGS) is rapidly being incorporated into the clinical management of biliary cancers. IHCCA is enriched with actionable mutations, and there are several promising targeted therapies under development. NGS data from Asia, where IHCCA is most prevalent, are limited. METHODS Comprehensive genomic profiling of formalin-fixed paraffin-embedded tumor tissue from 164 Asian and 283 Western patients with IHCCA was performed using NGS. We measured the distribution of DNA repair genetic aberrations (GAs) in IHCCA, along with actionable mutations. Also, we evaluated the association between DNA repair GAs and tumor mutation burden (TMB). Based on the TMB status, patients were distinguished into 3 levels: low (< 6 mut/Mb), intermediate (6-10 mut/Mb), and high (TMB-H; ≥ 10 mut/Mb). RESULTS Seventy-two percent of Asian patients had ≥ 1 actionable GA, with a significantly higher frequency in KMT2C , BRCA1/2, and DDR2 compared with Western patients ( P = .02, .003, and .003, respectively); 60.9% of Western patients had ≥ 1 actionable GA and higher frequency of CDKN2A/B and IDH1/2 GAs ( P = .0004 and < .001, respectively). GAs in nuclear factor kappa B pathway regulators and DNA repair genes occurred more frequently in Asian patients ( P = .006 and .001, respectively). There was a higher frequency of TMB-H in Asian compared with the Western cohort (12.2% v 5.9%; P = .07). CONCLUSION A higher burden of DNA repair mutations and frequency of patients with TMB-H in the Asian IHCCA cohort compared with the Western patients suggests a potential role for DNA repair and immune checkpoint inhibitors in the Asian population. Future clinical trials should account for this genetic heterogeneity.

4087 Background: The management of CCA has evolved as targeted and immune checkpoint inhibitor (ICPI) therapies have emerged. We used comprehensive genomic profiling (CGP) to characterize the genomic alterations (GA) that have potential to personalize therapy for CCA. Methods: 3634 CCA underwent hybrid capture based CGP on 0.8-1.1 Mb of the coding genome to identify GAs in exons and select introns in up to 404 genes, TMB, microsatellite status (MSI) and % monoallelic genome (gLOH). PD-L1 expression was determined by IHC (Dako 22C3). Results: 52% of CCA were female with a median age of 62 years (range 16 - > 89). The most common biopsy sites were liver (74%), lymph node (4%), bile duct (3.3%), and lung (2%). MSI-high was rare (1%), 118 and 47 cases had TMB > 10 and > 20 mut/mb respectively. Of the latter, 51% (24/47) were MSI-H. PD-L1 amplification (AMP) was present in 0.27%. Of 490 CCA tested, 43 (9%) were positive for PD-L1 expression. 11% of cases had gLOH > 16%, only 2 cases had both TMB > 20 and gLOH > 16%. GA were most common in TP53 (31%), CDKN2A (29%), KRAS (20%) and ARID1A (17%). Potentially targetable GAs included FGFR2 (11%, 85% fusions), BRAF (5%, 50% V600E), ERBB2 (5%, 72% AMP), MET (2%, 90% AMP), EGFR (0.52%) and rarer ( < 0.5%) FGFR3, RET, FGFR1, ALK, and ROS1 fusions. The FGFR2 fusions had 128 unique 3’ partner genes including BICC1 (26%), CCDC6 (3.2%), AHCYL1 (2.6%) and KIAA1217 (2.6%). FGFR2 fusions occurred in a mutually exclusive fashion from high gLOH (p < 0.002), but not high TMB. GA in IDH1 (15%) were mutually exclusive of FGFR2 fusions (p < 1e-13), but co-occurred with PBRM1 GA (23%, p < 1e-21), ARID1A (26% p < 1e-10). IDH1 GA had gLOH similar to the overall CCA population but were enriched for low TMB (p < 1e-3). Conclusions: Nearly 20% of CCA cases harbor targetable kinase GA, half of which were FGFR2 fusions. Independently, an additional 10% (gLOH) and 1% (high TMB, MSI and/or PD-L1 AMP) may benefit from PARP inhibitors and ICPI respectively. Independently, co-mutation of IDH1 and PBRM1/ARID1A defines a class of CCA that warrants further investigation for sensitivity to PARP inhibitors and may serve as a paradigm for other tumors (ie. gliomas) with a similar co-occurrence landscape.

263 Background: DNA repair genomic alterations (GAs) have been identified in 12% of Intrahepatic cholangiocarcinoma (IHCCA), 26% of extrahepatic CCA (EHCCA) and 8% of gallbladder cancer (GBC) patients (pts) ( Cancer 2016;122:3838–3847). Recently, the Cancer Genome Atlas (TCGA) has described more than 20 mutated DNA repair genes, many of which were not previously represented in prior reports. DNA repair GAs including MSI are associated with higher tumor mutational burden (TMB). Our study aim is to identify variations in the frequency of DNA repair GAs in IHCCA, EHCCA, and GBC. Methods: Hybrid capture-based next-generation sequencing of 422 fixed formalin paraffin embedded (FFPE) tissue blocks of BTC including; 270 IHCCA, 60 EHCCA, and 92 GBC was performed. We included 20 DNA repair genes and classified them as "direct" DNA repair genes ( ATM, ATR, BRCA1, BRCA2, FANCA, FANCD2, MLH1, MSH2, MSH6, PALB2, POLD1, POLE, PRKDC, RAD50, SLX4) and "caretaker" genes that induce genomic instability ( BAP1, CDK12, MLL3, TP53, BLM). We calculated TMB on 1.1 Mb of sequenced DNA in 205 tissue specimens [138 IHCCA, 23 EHCCA, and 44 GBC] and classified into three groups; high (TMB-H; ≥ 20 mut/Mb), intermediate (TMB-I; 6-19mut/Mb) and low (TMB-L; < 6mut/Mb). Results: A distinct pattern of DNA repair GAs in each tumor type was detected. (Table 1). DNA repair GAs were more commonly noted in both EHCCA and GB (63%) as compared with IHCAA (45.2%) (p= .002). Direct DNA repair GAs were highest within EHCCA (25%), while indirect DNA GAs were predominant in GBC (59.8%) (p= 0.04 and 0.001, respectively). The frequency of TMB-H and TMB-I differed significantly between BTC subtypes. Pts with EHCCA and GBC had significantly higher TMB-H and TMB-I versus IHCCA. Conclusions: The frequency of DNA repair GA’s is higher in EHCCA and GBC as compared with IHCCA. These results may have implications for clinical trials with DNA repair inhibitors and immune checkpoint blockers. [Table: see text]

Purpose FGFR genetic aberrations (GAs) occur in an estimated 10% to 16% of intrahepatic cholangiocarcinomas (CCAs). The natural history of CCA with FGFR GAs, the prognostic role of coexisting GAs, and the outcome with FGFR-targeted inhibitors are unknown. Patients and Methods Patients with CCA with FGFR GAs were identified using next-generation sequencing or fluorescence in situ hybridization from four tertiary cancer centers and compared with FGFR wild-type counterparts. Data reviewed included demographic, treatment, overall survival (OS), and GA data. Fisher’s exact test, Kaplan-Meier plots, and log-rank tests were used for statistical analysis. Results Three hundred seventy-seven patients with CCA were identified, and 95 had FGFR GAs. FGFR2 GA was most common (n = 74, with 63 fusions) and seen in intrahepatic CCA. In patients with CCA, FGFR GAs occurred more frequently in younger patients (≤ 40 years; 20%) compared with older patients (> 40 years; 6.7%; P < .001), presented at an earlier stage (TNM stage I/II v III/IV: 35.8% v 22%, respectively; P = .001), and were associated with a longer OS compared with patients without FGFR GAs (37 v 20 months, respectively; P < .001). This difference remained significant after excluding 36 patients treated with FGFR inhibitors. There was no OS difference ( P = .60) between CCA with FGFR2 fusions (n = 63) versus other FGFR GAs (n = 29). Patients with FGFR GAs had a better OS with FGFR-targeted therapy compared with standard treatment ( P = .01). BAP1 mutation was the most common coexisting mutation without prognostic impact, whereas TP53 ( P = .04) and CDKN2A/B ( P = .04) were correlated with a shorter OS. Conclusion CCA with FGFR GAs represents a unique subtype occurring in younger patients with an indolent disease course. FGFR-targeted therapy may have a positive impact on OS in this subgroup.