Mutant KRAS and GNAS DNA Concentrations in Secretin-Stimulated Pancreatic Fluid Collected from the Pancreatic Duct and the Duodenal Lumen

OBJECTIVES: The analysis of secretin-stimulated pancreatic fluid is being evaluated as an approach to improve the early detection of pancreatic cancer and pancreatic precursor neoplasms. The method of pancreatic fluid sampling may have a significant impact on tumor marker measurements. The aim of this study was to compare concentrations of mutant DNA in pancreatic fluid from patients who had samples collected from both the pancreatic duct and duodenal lumen. METHODS: Thirty-six participants enrolled in the Cancer of the Pancreas Screening studies at Johns Hopkins Hospital who had secretin-stimulated pancreatic fluid collected from the duodenum during endoscopic ultrasound (EUS) and from the pancreatic duct during subsequent endoscopic retrograde cholangiopancreatography. Mutant KRAS and GNAS DNA concentrations were measured in pancreatic fluid samples using digital high-resolution melt-curve analysis and pyrosequencing and were related total DNA concentrations in these samples. RESULTS: Thirty-four patients had subtle parenchymal abnormalities by EUS; seven had small pancreatic cysts; none had pancreatic cancer. KRAS mutations were detected in 29 of 36 (80.6%) pancreatic duct fluid samples. Of these 29 patients, 23 had mutations detected in their duodenal fluid (79.3%). Patients with detectable pancreatic fluid but not duodenal fluid KRAS mutations had lower average pancreatic duct fluid KRAS mutation concentrations (P=0.01). Patients with KRAS or GNAS mutations detected in pancreatic fluid but not duodenal fluid had higher total DNA concentrations in their duodenal compared with pancreatic fluid (P=0.03). KRAS and GNAS mutation concentrations were higher in pancreatic duct fluid samples than in matching duodenal fluid samples (for KRAS: 2.62 vs. 0.39%, P<0.0001). CONCLUSIONS: KRAS and GNAS mutation concentrations are significantly lower in secretin-stimulated pancreatic fluid samples collected from the duodenum compared with samples collected from the pancreatic duct. Efforts to improve the purity of pancreatic fluid collections from the duodenum could improve the detection of mutations arising from the pancreas.