This work aimed to contribute to the evaluation of a liquid biopsy approach in pancreatic cancer management and explored this method for prognostic patient stratification as well as treatment monitoring and tumor response evaluation. For this purpose, a suitable cell-free DNA (cfDNA) isolation method was identified and then digital droplet Polymerase chain reaction (ddPCR) mutant Kirsten Rat Sarcoma Gene (KRAS) detection was performed on advanced pancreatic ductal adenocarcinoma (PDAC) patient samples before and during chemotherapeutic treatment. In contrast to two other DNA isolation kits, the Maxwell cfDNA isolation kit was found to be most suitable for circulating tumor DNA (ctDNA) isolation because it isolates exclusively smallfragmented DNA. Using this DNA isolation method, liquid biopsy assessment was feasible and in the majority of patients the KRAS mutations detectable in tumor tissue could also be confirmed in the plasma.
Moreover, without a cut-off value needed, the absence of mutant KRAS in plasma was associated with a better overall survival and this relation increased when mutant KRAS remained untraceable after treatment onset.
Finally, the explorative analysis of treatment monitoring by liquid biopsy was promising and in the majority of cases, albeit at limited case numbers, the KRAS dynamics mirrored the clinical course of the disease and detected tumor progress simultaneously or even earlier than the computed tomography (CT).
These findings emphasize the enormous potential of ctDNA mutant KRAS detection as a noninvasive tool for prognostic stratification and therapy monitoring in PDAC and should inspire and assist the design of further studies on this topic.