Endoscopic Ultrasound Guided Fine Needle Biopsy With a New Core Histology Needle Versus Conventional Fine Needle Aspiration.

Background:

Endoscopic ultrasound (EUS) is a well-established tool for the diagnosis and staging of many gastrointestinal conditions, including but not limited to, malignant and pre-malignant neoplasms of the pancreas, esophagus, rectum, and submucosal tumors developing along the gastrointestinal tract. EUS provides endoscopic video imaging within the lumen of the gastrointestinal tract combined with ultrasound images via a transducer positioned at the tip of the endoscope. This diagnostic ability is enhanced by a biopsy method called fine needle aspiration (FNA). FNA via EUS (EUS-FNA) enables a small needle to be passed into a lesion of interest under ultrasound guidance, obtaining cellular material for cytology analysis. EUS-FNA is currently recommended for the confirmation of locally advanced pancreas adenocarcinoma, for the diagnosis of pancreatic cystic neoplasms and neuroendocrine tumors as well as autoimmune pancreatitis, for the characterization of submucosal tumors of the GI tract, and for the determination of malignant lymph node status in the staging of various cancers.

While EUS-FNA has an impressive technical success rate between 90-95%, the diagnostic accuracy is less robust for mass lesions, and in particular for pancreatic masses, for which the sensitivity and specificity is 75% and 100% respectively, translating into a negative predictive value of only 72%. And in the setting of chronic pancreatitis, a condition that is itself a major risk factor for the development of cancer and in which focal, non-malignant nodules often develop that may mimic tumors, the sensitivity of EUS-FNA may only be 54-74%. The diagnostic accuracy of EUS-FNA is of particular importance for pancreas adenocarcinoma and pancreatic neuroendocrine tumors because the 5-year survival rates are only 5% and 32% respectively. Thus, it is crucial that patients found to have a focal mass lesion have a reliable test that effectively excludes malignancy. Currently, EUS-FNA does not have the necessary negative predictive value in order to do so because the sensitivity of the test is too low. This means that a positive result on FNA confirms malignancy but that a negative result is unable to exclude it with confidence. This conundrum tends to leave the patient in the unfortunate position of having to often return for multiple investigations to perform repeat EUS-FNA when the clinical suspicion for a mass lesion remains high but the cytology result is thought to be falsely negative.

In order to overcome the current limitations of EUS-FNA cytology, the new EchoTip® ProCore™ fine needle biopsy (FNB) needle was developed in order obtain core tissue samples for both histology and cytology. This is important because histology is expected to increase the diagnostic yield of EUS-guided biopsy compared to cytology. In addition, in certain clinical circumstances it is more desirable and sometimes necessary to obtain a core tissue biopsy for histology rather than cellular material for cytology obtained with EUS-FNA.

In addition to the assessment of mass lesions in the pancreas, there are several other clinical areas in which the acquisition of core tissue samples for histology may prove superior to cytology from conventional EUS-FNA. For instance, EUS is part of the standard-of-care for the staging of esophageal cancer and histology may improve the sensitivity of EUS-biopsies for the determination of lymph node metastases. Also, although EUS is the preferred method for the work-up of submucosal lesions in the gastrointestinal tract, the value of EUS-FNA for differentiating the various subtypes of lesions is often limited, typically because FNA provides insufficient cellular material to reliably do so. Finally, it is clear that cytology from EUS-FNA is inadequate for the diagnosis of autoimmune pancreatitis and that a core biopsy sample for histology is needed. We expect the new EchoTip® ProCore™ FNB needle to potentially prove superior to FNA in all of these areas.