LAUSR

299Background: Current blood-based biomarkers for neuroendocrine tumors are limited. We performed a multi-stage study to identify characteristic circulating miRNAs in patients with advanced small intestine neuroendocrine tumors, and to assess associations between miRNA levels and survival. Methods: Using a 742-miRNA panel, we identified candidate miRNAs similarly expressed in 19 small intestine neuroendocrine tumors and matched plasma samples. We refined our panel in an independent cohort of plasma samples from 40 patients with advanced small intestine NET and 40 controls, and validated this panel in a second cohort of 120 patients and 120 controls. Results: miRNA profiling of 19 tumors and matched plasma samples revealed 31 candidate miRNAs similarly expressed in both tissue and plasma. We evaluated expression of these 31 candidate miRNAs in 40 independent cases and 40 normal controls, and identified 4 miRNAs (miR-21-5p, miR-22-3p, miR-29b-3p, and miR-150-5p) that were differently expressed in cases and ...