The Accurateness of Endoscopic Ultrasound Elastography in the Guidance of EUS-FNA in Solid Pancreatic Lesions

Pancreatic cancer is one of the leading causes of cancer-related death. It has a poor 5-year survival rate of around8-9%. This is primarily because of most patients with pancreatic adenocarcinoma progress to either metastatic or locally advanced disease while in the asymptomatic phase. However, if pancreatic cancer is detected in the early stage (i.e., less than 2.0 cm), it has a relatively better prognosis.

Traditionally, transabdominal ultrasound or computed tomography CT scanning are used to diagnose pancreatic lesions. However, transabdominal ultrasound is limited because it cannot be used to visualize the entire pancreas due to intervening fat or air. Endoscopic ultrasonography (EUS) is currently an essential emerging tool for the work-up of pancreaticobiliary neoplasms. (EUS) is an ultrasound (US) technique in which the tip of the endoscope is equipped with a high-frequency transducer. High-resolution images of the pancreas can be obtained through the esophagus, stomach, and duodenum, without the disrupting effects of intervening gas, fat, and bone. EUS is now regarded as the most sensitive imaging modality for the detection of even a very small pancreatic lesion. Endoscopic ultrasound (EUS) elastography is a novel non-invasive technique that is used for the evaluation of pancreatic tissue which was first reported in 2006 and can be used for distinguishing benign from malignant pancreatic masses. Therefore, accurate detection of small cancers is important for reducing the mortality rate from pancreatic cancer. The equipment can be coupled with conventional EUS without the need for additional devices. There are two types of EUS elastography, strain and shear wave. Strain elastography estimates the stiffness and elasticity of the target tissue by measuring the degree of strain produced in response to compression. Shear wave elastography involves the emission of focused ultrasound from the probe to the target tissue, the so-called 'acoustic radiation force impulse' (ARFI), and the stiffness of the target tissue is then estimated by measuring the propagation speed of the shear wave. Only strain elastography is so far available for EUS. EUS elastography is used to characterize pancreatic masses and lymph node metastases of pancreatic cancer as well as to judge the severity of chronic pancreatitis with the evaluation of lesion elasticity EUS-guided fine needle aspiration (EUS-FNA) has been generally used for the sampling of pancreatic tissues since it was first reported in 1992. In general, 19G-25G caliber needles are inserted under EUS guidance for the pathological diagnosis of pancreatic cancer and lymph nodes and/or hepatic focal lesions. The overall complication rate of EUS-FNA is including complications such as pain, bleeding, and pancreatitis.

EUS FNA remains the gold standard in diagnosing pancreatic lesions and pancreatic cancer via tissue acquisition with a sensitivity of 80-85% and a specificity of 100 %, however, the diagnostic accuracy of EUS guided FNA is limited and EUS FNA can be associated with risks and complications. Many pre-procedural and procedural considerations must be assessed before performing EUS guided FNA. The location of the lesion, lack of adequate visualization, lack of experience of the endoscopist, lack of onsite pathology, and lack of adequate sampling are all limitations in diagnostic yield. False negatives can also occur in up to 40% of cases. In our multi-center experience, we are going to focus on the use of EUS elastography to direct the site of fine-needle aspiration in tissue acquisition of solid pancreatic lesions and its effect on the accuracy of diagnosis and detection of solid pancreatic lesions.