Liquid biopsy of wash samples obtained via endoscopic ultrasound‐guided fine‐needle biopsy: Comparison with liquid biopsy of plasma in pancreatic cancer

Abstract Objectives Pancreatic cancer (PC) has a poor prognosis and limited treatment options. Liquid biopsy, which analyzes circulating tumor DNA (ctDNA) in blood, holds promise for precision medicine; however, low ctDNA detection rates pose challenges. This study aimed to investigate the utility of wash samples obtained via endoscopic ultrasound‐guided fine‐needle biopsy (EUS‐FNB) as a liquid biopsy for PC. Methods A total of 166 samples (42 formalin‐fixed paraffin‐embedded [FFPE] tissues, 80 wash samples, and 44 plasma samples) were collected from 48 patients with PC for genomic analysis. DNA was extracted and quantified, and 60 significantly mutated genes were sequenced. The genomic profiles of FFPE tissues, wash samples, and plasma samples were compared. Finally, the ability to detect druggable mutations in 80 wash samples and 44 plasma samples was investigated. Results The amount of DNA was significantly lower in plasma samples than in wash samples. Genomic analysis revealed a higher detection rate of oncogenic mutations in FFPE tissues (98%) and wash samples (96%) than in plasma samples (18%) and a comparable detection rate in FFPE tissues and wash samples. Tumor‐derived oncogenic mutations were detected more frequently in wash samples than in plasma samples. Furthermore, the oncogenic mutations detection rate remained high in wash samples at all PC stages but low in plasma samples even at advanced PC stages. Using wash samples was more sensitive than plasma samples for identifying oncogenic and druggable mutations. Conclusions The wash sample obtained via EUS‐FNB is an ideal specimen for use as a liquid biopsy for PC.