Side-by-side comparison of next-generation sequencing, cytology, and histology in diagnosing locally advanced pancreatic adenocarcinoma

Background and Aims: EUS-guided biopsy sampling is the method of choice for obtaining pancreatic tissue. Next-generation sequencing (NGS) has been applied to EUS-guided biopsy sampling and may classify patients based on specific molecular profiles. Our study aimed to compare side-by-side the diagnostic yield achievable by genetic identification of somatic mutations detected with NGS versus histologic and cytologic typing in locally advanced pancreatic carcinoma (LAPC) in samples acquired under EUS guidance. Methods: We conducted a prospective comparative pilot study at Humanitas Research Hospital. The study included 33 patients referred for LAPC who underwent EUS-guided tissue acquisition using a 22-gauge Franseen needle. Material was obtained for both pathologic diagnosis and DNA extraction and targeted NGS analysis with the AmpliSeq Comprehensive Panel v3 (Illumina Inc, San Diego, Calif, USA). Twenty-one genes were prioritized for somatic mutation detection. Results: The final diagnosis was pancreatic ductal adenocarcinoma (PDAC) in all patients (100%). A macroscopic core was obtained in 30 patients (91%). In 3 lesions no cores adequate for histologic analysis were obtained, but cytologic analysis revealed tumoral cells from PDAC. DNA was extracted from 32 of 33 samples (97%), most of which (27/32) carried at least 2 clearly pathogenic mutations in different genes. Detection of K-ras mutation allowed for molecular diagnosis of PDAC in most of the patients (30/32). Conclusions: In our study we demonstrated that proper tissue specimens obtained under EUS guidance allowed DNA sample extraction and subsequent NGS analysis in 97% of cases. These results support the potential role of NGS as a complementary diagnostic test to be implemented in association with standard diagnostic modalities. (Clinical trial registration number: NCT03578939.)