Mutant KRAS in Circulating Tumor DNA as a Biomarker in Localized Pancreatic Cancer in Patients Treated with Neoadjuvant Chemotherapy

Objective: The primary objective was to determine the prognostic significance of circulating tumor DNA (ctDNA) in patients receiving neoadjuvant chemotherapy (NAC) for localized pancreatic ductal adenocarcinoma (PDAC) using digital droplet polymerase chain reaction (ddPCR). Summary and Background Data: Increasingly, ctDNA is being used for clinical decision-making in a variety of solid malignancies. However, the detection and prognostic value of KRAS ctDNA as assessed by ddPCR during NAC has yet to be characterized. Methods: Patients with localized PDAC eligible to receive NAC were prospectively enrolled. Peripheral blood samples were obtained at diagnosis, after NAC, and after resection and analyzed for ctDNA using ddPCR. Log-rank tests and Cox proportional hazards model were used to assess for association with OS. Results: 84 patients were included in the analysis. Mutant KRAS ctDNA was detected in 49.3% of patients at diagnosis, 69.6% of patients after NAC, and 69.7% of patients after resection, respectively. There were 15 (17.9%) patients that cleared mutational ctDNA over the course of treatment. Clearance of ctDNA during NAC was associated with improved overall survival (OS) (18.4 mo. vs NR, P <0.05). Detection of mutant KRAS G12V after NAC and resection was associated with shorter OS (18.0 versus NR months, P <0.031). Detection of the KRAS G12V mutation after resection was associated with reduced OS (aHR 36.75, 95% CI 2.93-461.38). Conclusions: Throughout treatment, KRAS ctDNA is detectable by ddPCR in patients with localized PDAC treated with NAC. Detection of mutant KRAS G12V after resection was associated with reduced OS.