Characterization of Blood-Based Molecular Profiling in Pancreatic Adenocarcinoma

Background: Molecular profiling is being explored in pancreatic adenocarcinoma (PDAC) as a tool to assist with early detection, prognosis, and patient selection in targeted therapy clinical trials. Due to the challenges and risks of traditional tissue biopsies in pancreatic adenocarcinoma, the utility of blood-based molecular profiling is now being explored more broadly. However, given its novelty, what value blood-based molecular profiling may provide to oncologists caring for individuals with PDAC remains unknown. Herein, we characterize the mutational landscape of metastatic PDAC using blood-based circulating tumor DNA (ctDNA) collected in patients with refractory, metastatic PDAC who were referred to an oncology drug development unit in Denver, Colorado, between August 2014 and May 2019. Methods: We retrospectively analyzed results of blood-based molecular profiling that was performed on 77 consecutive patients with metastatic PDAC who underwent Guardant-360 testing for whom results were available. Results: In our data set, 55% of patients (41/77) were men, median (SD) age was 66 (9.3) years (range, 44-83). Of 77 patients, 34 (44%) had 1 or more somatic alterations. Variants reported as being of unknown significance were not included in the analyses. The total number of alterations were 119 (nonunique) and 96 (unique). The median number of alterations per patient was 3 and the median mutant allele frequency was 0.5%. TP53 was the most commonly altered gene (29 unique alterations), followed by KRAS (27 unique alterations). Of the patients with any alteration, 34% had 1 or more actionable alterations that could be potentially targeted in a clinical trial. Conclusions: Detection of genomic alterations in ctDNA from patients with metastatic PDAC is feasible and reveals a wide range of genomic alterations, the actionability of which is being explored in clinical trials. Further investigation is needed to determine the extent to which blood-based molecular profiling can provide clinical utility in helping to select patients into clinical trials and determine its impact on survival.