ABSTRACT: BACKGROUND:Appendiceal cancers (ACs) are rare. The genomic landscape of ACs has not been well studied. The aim of this study was to confirm the feasibility of next-generation sequencing (NGS) using circulating tumor DNA (ctDNA) in ACs and characterize common genomic alterations. MATERIALS AND METHODS:Molecular alterations in 372 plasma samples from 303 patients with AC using clinical-grade NGS of ctDNA (Guardant360) across multiple institutions were evaluated. Test detects single nucleotide variants in 54-73 genes, copy number amplifications, fusions, and indels in selected genes. RESULTS:A total of 303 patients with AC were evaluated, of which 169 (56%) were female. Median age was 56.8 (25-83) years. ctDNA NGS testing was performed on 372 plasma samples; 48 patients had testing performed twice, 9 patients had testing performed three times, and 1 patient had testing performed four times. Genomic alterations were defined in 207 (n =?207/372, 55.6%) samples, and 288 alterations were identified excluding variants of uncertain significance and synonymous mutations. Alterations were identified in at least one sample from 184 patients; TP53-associated genes (n =?71, 38.6%), KRAS (n =?33, 17.9%), APC (n =?14, 7.6%), EGFR (n =?12, 6.5%), BRAF (n =?11, 5.9%), NF1 (n =?10, 5.4%), MYC (n =?9, 4.9%), GNAS (n =?8, 4.3%), MET (n =?6, 3.3%), PIK3CA (n =?5, 2.7%), and ATM (n =?5, 2.7%). Other low-frequency but clinically relevant genomic alterations were as follows: AR (n =?4, 2.2%), TERT (n =?4, 2.2%), ERBB2 (n =?4, 2.2%), SMAD4 (n =?3, 1.6%), CDK4 (n =?2, 1.1%), NRAS (n =?2, 1.1%), FGFR1 (n =?2, 1.1%), FGFR2 (n =?2, 1.1%), PTEN (n =?2, 1.1%), RB1 (n =?2, 1.1%), and CDK6, CDKN2A, BRCA1, BRCA2, JAK2, IDH2, MAPK, NTRK1, CDH1, ARID1A, and PDGFRA (n =?1, 0.5%). CONCLUSION:Evaluation of ctDNA is feasible among patients with AC. The frequency of genomic alterations is similar to that previously reported in tissue NGS. Liquid biopsies are not invasive and can provide personalized options for targeted therapies in patients with AC. IMPLICATIONS FOR PRACTICE:The complexity of appendiceal cancer and its unique genomic characteristics suggest that customized combination therapy may be required for many patients. Theoretically, as more oncogenic pathways are discovered and more targeted therapies are approved, customized treatment based on the patient's unique molecular profile will lead to personalized care and improve patient outcomes. Liquid biopsies are noninvasive, cost-effective, and promising methods that provide patients with access to personalized treatment.
