Endoscopic Ultrasonography (EUS) Strain Ratio (SR-EUS) vs. Contrast-Enhanced EUS (CE-EUS) for the Diagnosis of Focal Pancreatic Solid Lesions

Abstract

Background: There are many difficulties in the differential diagnosis between pancreatic cancer and chronic pancreatitis despite recent progress. As a means of trying to overcome this in the endossonography field, the measurement of the tissue stiffness (elastography) by new image processors and the use of contrast agent to enhance the color Doppler pattern have been introduced. Aims: Our aim is to compare prospectively the ability of the SR-EUS and CE-EUS to differentiate between benign and malignant focal pancreatic lesions. Methods: Thirty-eight patients with a focal pancreatic lesion were included to date. EUS procedures were performed with linear-array echoendoscopes (FG36X or EG38UT, Pentax), an ultrasound platform (Hitachi 7500 or 8500) with an integrated elastography module. In order to obtain the SR-EUS, a circular area is adjusted to the focal lesion and a second one is adjusted to the surrounding tissue. The SR-EUS (focal lesion area strain % / surrounding tissue area strain %) is calculated. After elastography, SonoVue® 2.4 mL (Bracco) was injected intravenously at a rate of 1 ml/sec, following a flash of 10mL saline solution. The pattern of enhancement (hypo or hypervascular) was defined using power Doppler mode. EUS-FNA was performed by using a 22-gauge FNA needle (Echotip, Cook Endoscopy,). The final diagnosis was based on the histological assessment of the EUS-FNA samples and/or surgical specimens when available. A positive cytological diagnosis was taken as a final proof of malignancy. For negative cytological specimens, the diagnosis was confirmed by surgery or follow-up of at least six months. Results: The study population comprised 21 (55%) men, mean age 62±16 years, with 12 (32%) benign and 26 (68%) malignant pancreatic lesions. Univariate analysis determined that the variables associated with malignancy included lesion size, SR-EUS and CE-EUS (Table). Logistic regression analysis determined that hypovascular lesions at CE-EUS (odds ratio 6.2 [95% CI, 1.2-32.1], p=0.03) was the only variable independently predictive of malignant pancreatic lesion. Conclusion: In this small group, CE-EUS was superior to SR-EUS for the differentiation between benign and malignant focal pancreatic lesions.