Bead-Based Isolation of Circulating Tumor DNA from Pancreatic Cancer Patients Enables High Fidelity Next Generation Sequencing

INTRODUCTION: Pancreatic ductal adenocarcinoma (PDAC) is one of the most aggressive cancers and poses a challenge to the treating clinician. With the emergence of genomic profiling technologies, circulating tumor DNA (ctDNA) is increasingly recognized as a versatile biomarker for risk stratification and disease monitoring. We aimed to compare two commercially available NGS panels in a cohort of patients with advanced PDAC undergoing palliative chemotherapy. METHODS: CtDNA was isolated with a magnetic bead-based protocol from two consecutive blood samples before and during chemotherapy in 21 patients with PDAC. Mutations were assessed by using a panel covering 15 (GP15) or 50 (GP50) cancer-associated genes. Results were compared to tumor tissue (GP15), if available. RESULTS: Isolation of ctDNA resulted in a high mean value of 1.9 ng/µL (total volume of ~40 µL). Although the same number of patients were positive for at least one mutation (76%), the most commonly mutated oncogene in PDAC, KRAS, was detectable in an additional 25% of all patients with the GP15 panel due to a higher coverage. The genomic concordance rate between tissue DNA and ctDNA analyses was 65.22%. DISCUSSION: Our study demonstrates the feasibility of an NGS-based approach for ctDNA analysis and underlines the importance of using a disease-specific panel with a sufficiently high coverage.