Circulating Free Tumor Dna Copy Number Index (Cni) As A Predictor Of Therapeutic Response In Pancreatic Ductal Adenocarcinomas (Pdac)

261Background: Cell-free tumor DNA (cfDNA) has potential to provide minimally invasive patient specific biomarkers to monitor tumor burden. Tumor-specific copy number instability (CNI) are used to quantify tumor-derived cfDNA in the plasma. We prospectively computed CNI Scores of cfDNA to compare with radiological and Ca 19-9 responses. Methods: In a laboratory blinded, prospective single-institution study, 119 plasma samples from 33 patients (pts) with PDAC were analyzed. Time-points were at baseline (C1), 2nd (C2) and 3rd (C3) cycle of systemic therapy. Tumor cfDNA was measured with a CNI scoring assay that quantifies cfDNA with somatic macro-alterations. CNI Score (CNIs) of 31 was defined as ref. range (97.5 % - control group; N = 135), pts below this threshold were censored. Progression of disease (PD) defined as C3 CNIs u003e 93 (3-fold threshold) and difference to the baseline u003e 31 (dispersion of reference population). Mutant KRAS in plasma was measured using ddPCR in a subset 22 pts. Pts with an increa...