Pancreatic ductal adenocarcinoma (PDAC) is an aggressive malignancy with a poor prognosis, and current diagnostic tests have suboptimal sensitivity. Incorporating standard cytology with targeted transcriptomic and mutation analysis may improve upon the accuracy of diagnostic biopsies, thus reducing the burden of repeat procedures and delays to treatment initiation.
We reviewed the accuracy of 308 endoscopic ultrasound-guided fine-needle aspiration (EUS-FNA) diagnostic PDAC biopsies using a large multicenter clinical and biospecimen database, then performed RNA sequencing on 134 EUS-FNA biopsies spanning all stages of disease. We identified a transcriptomic diagnostic gene signature that was validated using external datasets and 60 further diagnostic EUS-FNAs. KRAS digital droplet PCR (ddPCR) analysis was performed and correlated with signature gene expression.
The sensitivity of EUS-FNA cytology in diagnosing solid pancreatic masses in our retrospective cohort of 308 patients was 78.6% (95% confidence interval, 73.2%–83.2%). KRAS mutation analysis and our custom transcriptomic signature significantly improved upon the diagnostic accuracy of standard cytology to 91.3% in external validation sets and 91.6% in our validation cohort (n = 60). Exploratory ddPCR analysis of KRAS-mutant allele fraction (MAF%) correlated closely to signature performance and may represent a novel surrogate marker of tumor cellularity in snap-frozen EUS-FNA biopsies.
Our findings support snap-frozen EUS-FNA biopsies as a feasible tissue source for the integrated genomic and transcriptomic analysis of patients presenting with PDAC from all tumor stages, including cases with nondiagnostic cytology. Our transcriptome-derived genetic signature in combination with tissue KRAS mutation analysis significantly improves upon the diagnostic accuracy of current standard procedures, and has potential clinical utility in improving the speed and accuracy of diagnosis for patients presenting with PDAC.