Prospective Study
Copyright ©The Author(s) 2015. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Gastroenterol. Apr 7, 2015; 21(13): 4014-4019
Published online Apr 7, 2015. doi: 10.3748/wjg.v21.i13.4014
Endoscopic ultrasound elastography strain histograms in the evaluation of patients with pancreatic masses
Dalibor Opačić, Nadan Rustemović, Mirjana Kalauz, Pave Markoš, Zvonimir Ostojić, Matea Majerović, Iva Ledinsky, Ana Višnjić, Juraj Krznarić, Milorad Opačić
Dalibor Opačić, Zvonimir Ostojić, Clinical Hospital Center Zagreb, 10000 Zagreb, Croatia
Nadan Rustemović, Mirjana Kalauz, Pave Markoš, Matea Majerović, Milorad Opačić, Division of Gastroenterology, Clinical Hospital Center Zagreb, 10000 Zagreb, Croatia
Iva Ledinsky, Clinic for Tumors, Clinical Hospital Center “Sisters of Mercy”, 10000 Zagreb, Croatia
Ana Višnjić, Juraj Krznarić, Medical Faculty University of Zagreb, 10000 Zagreb, Croatia
Milorad Opačić, Department of Internal Medicine, Division of Gastroenterology, University Hospital Center Zagreb, 10000 Zagreb, Croatia
Author contributions: Opačić D, Rustemović N and Kalauz M designed the research and supervised realization of the manuscript; Markoš P, Ostojić Z and Majerović M wrote the paper; Ledinsky I, Višnjić A and Krznarić J collected and analyzed data and contributed to technical support; Opačić M critically revised the manuscript for important intellectual content; all the authors gave their approval to the final version to be published.
Supported by Croatian Ministry of Science, project number 0214214.
Open-Access: This article is an open-access article which was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/
Correspondence to: Milorad Opačić, MD, Assistant Professor, Department of Internal Medicine, Division of Gastroenterology, University Hospital Center Zagreb, Kispaticeva 12, 10000 Zagreb, Croatia. opacic.m@gmail.com
Telephone: +385-1-2388041 Fax: +385-1-2376027
Received: August 7, 2014
Peer-review started: August 8, 2014
First decision: August 27, 2014
Revised: October 2, 2014
Accepted: November 18, 2014
Article in press: November 19, 2014
Published online: April 7, 2015
Abstract

AIM: To investigate the accuracy of the strain histogram endoscopic ultrasound (EUS)-based method for the diagnostic differentiation of patients with pancreatic masses.

METHODS: In a prospective single center study, 149 patients were analyzed, 105 with pancreatic masses and 44 controls. Elastography images were recorded using commercially available ultrasound equipment in combination with EUS linear probes. Strain histograms (SHs) were calculated by machine integrated software in regions of interest and mean values of the strain histograms were expressed as Mode 1 (over the mass) and Mode 2 (over an adjacent part of pancreatic tissue, representing the reference area). The ratio between Mode 2 and Mode 1 was calculated later, representing a new variable, the strain histogram ratio. After the final diagnosis was established, two groups of patients were formed: a pancreatic cancer group with positive cytology achieved by fine needle aspiration puncture or histology after surgery (58 patients), and a mass-forming pancreatitis group with negative cytology and follow-up after 3 and 6 mo (47 patients). All statistical analyses were conducted in SPSS 14.0 (SPSS Inc., Chicago, IL, United States).

RESULTS: Results were obtained with software for strain histograms with reversed hue scale (0 represents the hardest tissue structure and 255 the softest). Based on the receiver operating characteristics (ROC) curve coordinates, the cut-off point for Mode 1 was set at the value of 86. Values under the cut-off point indicated the presence of pancreatic malignancy. Mode 1 reached 100% sensitivity and 45% specificity with overall accuracy of 66% (95%CI: 61%-66%) in detection of pancreatic malignant tumors among the patients with pancreatic masses. The positive and negative predictive values were 54% and 100%, respectively. The cut-off for the new calculated variable, the SH ratio, was set at the value 1.153 based on the ROC curve coordinates. Values equal or above the cut-off value were indicative of pancreatic malignancy. The SH ratio reached 98% sensitivity, 50% specificity and an overall accuracy of 69% (95%CI: 63%-70%). The positive and negative predictive values were 92% and 100%, respectively.

CONCLUSION: SH showed high sensitivity in pancreatic malignant tumor detection but disappointingly low specificity. Slight improvements in specificity and accuracy were achieved using the SH ratio.

Keywords: Endoscopic ultrasound, Pancreatic cancer, Pancreatic mass, Elastography, Histogram, Pancreatic tumor, Mass-forming pancreatitis

Core tip: Endoscopic ultrasound quantitative elastography strain histograms (SHs) are a recently developed method for non-invasive differentiation of pancreatic masses. In a prospective single center study, 105 patients with pancreatic masses and 44 controls were evaluated. For SH measurements, Hitachi software was used and applied for the first time in a clinical study as far as we know. We determined the accuracy of the method and a cut-off value between malignant pancreatic tumors and mass-forming pancreatitis. A new variable, the SH ratio, is calculated in an attempt to improve the sensitivity, specificity and accuracy of the method.