Improving the diagnostic accuracy of endoscopic ultrasound-guided fine-needle aspiration using microRNAs.

Brand RE, Adai AT, Centeno BA, et al. A microRNA-based test improves endoscopic ultrasound–guided cytologic diagnosis of pancreatic cancer. Clin Gastroenterol Hepatol 2014;12:1717–1723. Owing to its safety profile, diagnostic accuracy, and low risk of tumor seeding, endoscopic ultrasound–guided fine-needle aspiration (EUS-FNA) represents the preferred modality for achieving a tissue confirmation of pancreatic ductal adenocarcinoma (PDAC; J Cancer Res Clin Oncol 2012;138: 1433–1441; Gastrointest Endosc 2003;58:690–595; Endoscopy 2011;43:897–912). In a recent metaanalysis that included 41 studies and 4766 procedures, EUS-FNA had a pooled sensitivity of 87% and specificity 96% for the diagnosis of malignant pancreatic lesions (Pancreas 2013;42: 20–26). However, the sensitivity of EUS-FNA is lower in the setting of chronic pancreatitis (CP), where false-negative rates may be as high as 40% (Gastrointest Endosc 2005;62: 728–736l; Gastrointest Endosc 2009;70:70–79). Thus, there is substantial interest in improving the accuracy of cytopathology for diagnosing PDAC—and potentially informing long-term prognosis of this deadly cancer—using novel molecular markers such as microRNAs (miRNAs; Clin Cancer Res 2011;17:5812–5821). miRNAs are small, noncoding RNAs (17–25 nucleotides long) that regulate gene expression post-transcriptionally. These molecules are stable and easily recovered from tissue or blood, making EUS-FNA specimens suitable for analysis (Clin Chem 2008;54:1716–1724). Unique miRNA “signatures” have been evaluated using formalin-fixed, paraffin-embedded specimens, having >90% accuracy in distinguishing PDAC from CP and normal pancreata in limited studies (Clin Cancer Res 2011;17:5812–5821; Clin Chem 2008;54:1716–1724; Int J Cancer 2012;131:E86–95; Expert Rev Mol Diagn 2011;11:249–257). Using samples (n = 95) derived from formalin-fixed, paraffin-embedded tissues of PDAC and CP, Brand et al (Clin Gastroenterol Hepatol 2014;12:1717–1723) developed a miRNA panel and then analyzed its utility as a diagnostic test using pancreas tissue specimens (n = 229) derived from EUS-FNA. Starting with 11 candidate miRNAs applied to formalin-fixed, paraffin-embedded specimens (PDAC, n =52; CP, n = 43), the authors identified a panel of 5 miRNAs (−24, −130b, −135b, −148a, and −196a) having >95% agreement compared with standard histopathology when the miRNA classifier score was ≥0.5. Then, the authors applied this panel using polymerase chain reaction amplification techniques to EUS-FNA specimens prospectively collected at 8 participating centers. Only 1 FNA pass was dedicated for miRNA analysis, yet the rate of failed polymerase chain reaction amplification was only 1 in 229 (0.4%). Based on standard histopathology, the pretest probability of cancer was 202 in 228 (89%), with 184 of 202 cancers being PDAC (excluding non-PDAC cancers, the pre-test probability of PDAC was 184 of 202 [88%]). Although the prevalence of concomitant CP is not provided—the most common scenario in which the sensitivity of EUS-FNA is diminished—the sensitivity of cytopathology for detecting PDAC was 79% (145/184). By comparison, the miRNA panel correctly diagnosed PDAC in 152 of 184 patients (83%). The combination of cytopathology + miRNA resulted in a sensitivity/specificity of 167 of 184 (91%) and 25 of 26 (96%). Including 1 case of cholangiocarcinoma, the miRNA panel accurately detected adenocarcinoma in 130 of the 146 cases detected by cytopathology, with an 11% false-negative rate. In the setting of negative cytopathology and an miRNA panel score of <0.5, the posttest probability of PDAC (the false-negative rate of EUS-FNA cytopathology + miRNA) was 17 of 43 (40%). Because the sensitivity of achieving a diagnosis of PDAC increased from 79% using cytopathology alone to 91% when cytopathology was combined with an elevated miRNA panel, the authors concluded that a 5-miRNA classifier panel improves the performance characteristics of EUS-FNA.