Genomic architecture of gallbladder cancer: Results of a first prospective study.

Abstract

e16628 Background: Rarity in western countries precluded Gallbladder cancer (GBC) from prospective research. Comprehensive Genomic profiling carries potential to determine oncogenic pathways, driver mutations and possible resistance mechanisms. This study is evaluating the role of comprehensive genomic profiling and role of targeted therapies therein. Methods: This is a single center, prospective, study conducted from Aug2018-Dec2019. All consecutive patients of unresectable and/or metastatic GBC of age ≥18 years were enrolled. Hybrid capture based comprehensive genomic profiling was performed by Foundation Medicine CDx. Microsatellite instability and PDL1 expression were studied. Results: Median age was 56 years (range:26-83) with male to female ratio of 1:1.6. NGS information was available for 50 patients. ERBB pathway was aberrated in 44% of patients. ERBB2 & ERBB3 amplification was seen in 9(18%) and 2(4%) patients respectively. ERBB2 mutations were present concurrently with amplification in 3 patients. MET amplification was present in 3 (6%) PIK3CA mutations were seen in 14% of cases. PIK3CA mutations were independent of ERBB aberrations. FGFR2 mutation, FGFR2 and FGFR3 amplification was present in one patient each. NF1 and NF2 mutations were seen in three and two patients respectively. Median TMB (n = 39) was 5 mut/Mb with range of 1-14 mut/Mb. PDL1 (n = 31) of ≥ 1% was present in 32% of cases and it ranged from 1-100%. MSI (n = 39) was stable in all cases. Other somatic mutations and/or amplifications are shown in Table. Conclusions: GBC is enriched in 28% of patients with ERBB2 & ERBB3 amplifications and/or mutations. FGFR2 mutation is rare in GBC. PIK3CA aberrations are common. Phase 2 trial of frontline Trastuzumab combined with chemotherapy is ongoing. [Table: see text]