Next-generation sequencing reveals mutational accordance between cell-free DNA from plasma, malignant pleural effusion and ascites and directs targeted therapy in a gastric cancer patient.

Cell-free DNA (cfDNA) has been a research hotspot in molecular tumor profiling. In advanced gastric cancer patients, malignant pleural effusion (MPE) and ascites provide a wealth of tumor cells that can be investigated. Here we conducted next-generation sequencing (NGS) on matched cfDNA from plasma, MPE and ascites from a stage-IV gastric cancer patient to identify potential therapeutic targets. In all three samples, we detected an amplification in the cellular-mesenchymal to epithelial transition factor (MET) gene, a truncation mutation in SMAD3 (p.R368X), and four ataxia telangiectasia-mutated gene (ATM) variants, including a missense mutation (p.E2351A), an in-frame deletion (p.NPAVIM2353delinsK), a frame-shift deletion (p.D1758fs) and an ATM- BPI fold containing family B member 1 (BPIFB1) gene fusion. In contrast, we detected amplification of TEK only in malignant ascites. The patient was subjected to Crizotinib to counter MET amplification. Our study demonstrates high accordance in mutational spectra of matched cfDNA from plasma, MPE and ascites, and suggests that it is feasible to utilize these tumor sources in clinical decision-making.