Blood platelet RNA yields a new diagnostic prospective for accurate detection and staging of pancreatic ductal adenocarcinoma

Purpose: The analysis of tumor-educated platelets (TEPs) is gaining momentum for the detection of different tumor types in their early-stages. Here, we exploit spliced RNA profiles of tumor-educated platelet (TEPs) as a diagnostic and stage-specific biomarker for patients with pancreatic ductal adenocarcinoma (PDAC). Materials and methods: In our study, platelets of consecutive patients with PDAC (N=112) and benign hepatopancreaticobiliary diseases (N=60) were collected prospectively in two Amsterdam university medical centers (Amsterdam, The Netherlands) from January 2014. This study was conducted according to the Standards for Reporting Diagnostic Accuracy Studies (STARD), and all participants provided written informed consent. Platelet RNA was isolated and after quality assessment sequenced on Illumina Hiseq2500/4000, as described (Best et al, Nat Protol 2019). Particle-swarm optimization biomarker selection was used to develop the TEP-based PDAC diagnostic classifier and for construction of the stage-specific classifier. Diagnostic accuracy was defined by sensitivity and specificity, and accuracy was determined by the area under the receiver operating characteristic curve. Comparison of diagnostic accuracy with performance of CA19-9 was performed in paired patient samples. Results: The TEP-based diagnostic classifier resulted in an area under the curve (AUC) of 0.93 (95%CI=0.90-0.98) for detection of malignancy. The optimal cut-off of the TEP-score demonstrated a sensitivity of 71% at high specificity of 98%. TEP profiles outperformed the conventional tumor marker CA19-9 (AUC=0.84, 95%CI=0.77-0.91). By using the same platelet RNA repertoire, a stage-specific classifier was constructed, which allowed to distinguish early and late disease stages (AUC=0.91, 95%CI=0.86-0.97). Conclusions: RNA profiles of TEPs provide a novel tool to diagnose patients with PDAC using blood-based liquid biopsies. In addition, this study supports the use of TEPs for both diagnosis and staging of PDAC. Currently an independent cohort from Imperial College (London, UK) and Pisa University Hospital (Pisa, Italy) is being collected and evaluated for validation of the study.