LAUSR

47Background: Esophageal (EC), gastroesophageal junction (GEJ) and gastric cancer (GC), together GEC, have a poor prognosis with few targeted therapeutic options. As genomic profiling is becoming increasingly useful, we queried whether comprehensive genomic profiling of ctDNA would reveal relevant genomic alterations leading to targeted therapies. Methods: Patients (pts) with advanced GEC undergoing next-generation sequencing (NGS) of ctDNA in a CLIA certified lab were identified. ctDNA was analyzed using Guardant360, a digital NGS assay to identify single nucleotide variants, indels, amplifications and fusions in 54-70 genes. Results: 546 pts with GEC had ctDNA testing and 54 pts (10%) had more than one ctDNA test (range 2-6). Pts were similar across the 3 groups, with the exception of an increased male:female ratio (5:1) in the GEJ and EC cohorts. Mean age was 61.5 yrs (range 24-91). ctDNA alterations were detectable in 455 pts (83.3%). Recurrent alterations and therapeutic options for each cohort are s...