My Hospital Does Not Have an Endoscopic Ultrasonographer. Is It Safe for Me to Use Computed Tomography-Guided Fine Needle Aspiration for a Pancreatic Lesion?
Fine needle aspiration biopsy is a safe and minimally invasive method which may used to obtain a tissue diagnosis of a pancreatic lesion under imaging guidance. Other modalities for obtaining a biopsy of a pancreatic mass include computed tomography (CT), ultrasound, magnetic resonance imaging (MRI)-guided approaches, and, of course, laparoscopy or laparotomy-operative biopsy. Unfortunately, endoscopic ultrasound (EUS)-guided fine needle aspiration is not available at all hospitals.
The specificity of fine needle aspiration biopsy is less than perfect. Put simply, a negative biopsy result cannot be relied upon to exclude cancer. Therefore, the first question to ask oneself and to discuss with the surgeon who is to be involved is “Do we really need to subject the patient to a procedure in order to obtain a preoperative tissue diagnosis?” If there will be no change to management, and an operation will be performed in any event, then it may be reasonable to avoid a fine needle biopsy altogether.
Both CT and EUS have the ability to provide additional information aside from sampling for tissue. Each provides information about stage. EUS is particularly suited to the detection of peripancreatic lymph nodes and can sample them for their involvement. CT excels at defining vascular anatomy and detecting liver metastases of over 1 cm in size. Neither modality reliably detects metastatic deposits on the surface of the liver, or in the peritoneum, which may not be discovered until a laparoscopy.
When facing the choice between EUS as opposed to CT-guided fine needle aspiration biopsy techniques, the deciding factors include the safety and accuracy of the approach, the wishes of the patient, and the availability and expertise of the proceduralists and pathologists involved. The availability of on-site cytological evaluation is desirable. Some studies suggest that the 2 methods are equally effective for lesions both less than and greater than 3 cm.1-3 Others disagree: 1 retrospective study evaluated 1050 consecutive patients who underwent fine needle aspiration biopsy of the pancreas by ultrasound, CT-guided, or EUS-guided fine needle aspiration biopsies in a single institution. It was found that there was greater accuracy for EUS than ultrasound or CT for lesions less than 3 cm in size.4
Whenever I am deciding to send a patient out of hospital for a test elsewhere, I take into account the requirement for excellent and timely communication of the results, the risk of any delay that may be incurred, and finally the cost. Patients who have been informed that they have a mass in the pancreas are understandably anxious to have a firm diagnosis with accurate staging so that they may commence appropriate treatment as soon as possible. In my experience, patients often express concern regarding the risk of rapid tumor progression and may rush to the first available investigation, believing that any procedure is better than a diagnostic delay.
The risks of CT-guided fine needle aspiration biopsy for a pancreatic lesion include bleeding, pancreatitis, vasovagal reaction, tumor seeding, and pancreatic ductal fistula.5 The approach may be from anterior or from posterior. A coaxial needle may be used to sample even lesions that lie deep to the inferior vena cava or renal vein. Even when major veins, a renal artery, or the gastrointestinal tract is traversed by a needle, the risk of significant hemorrhage and peritonitis (even with transcolonic sampling) is extremely low.6 Tumor seeding is also an exceptionally rare occurrence.
The risks of EUS need to be taken into account when deciding which modality is best. These include the risks of sedation, perforation, pancreatitis, and bleeding. When using EUS, there are specific anatomic considerations such as ability to pass the scope, prevented, for example, by an esophageal stricture, or the presence of postoperative alterations in anatomy, such as gastric bypass surgery, which may prevent access to lesions in the head of the pancreas.
The efficacy and accuracy of EUS and CT has been assessed in several studies and the results vary.7,8 Some studies have suggested that the 2 modalities are equally able to safely sample all pancreatic lesions, regardless of size and location. Other studies do not. EUS-guided fine needle aspiration biopsy seems to have the edge for investigation of lesions less than 3 cm and may have advantages when investigating lesions that lie deep to intestine, arterial structures, inferior vena cava, and renal vein when approached under CT guidance.
1. Erturk SM, Mortele KJ, Tuncali K, Saltzman JR, Lao R, Silverman SG. Fine-needle aspiration biopsy of solid pancreatic masses: comparison of CT and endoscopic sonography guidance. American Journal of Roentgenology. 2006;187:1531-1535.
2. Horwhat JD, Paulson EK, McGrath K, et al. A randomized comparison of EUS-guided FNA versus CT or US-guided FNA for the evaluation of pancreatic mass lesions. Gastrointest Endosc. 2006;63:966-975.
3. Mallery JS, Centeno BA, Hahn PF, Chang Y, Warshaw AL, Brugge WR. Pancreatic tissue sampling guided by EUS, CT/US, and surgery: a comparison of sensitivity and specificity. Gastrointest Endosc. 2002;56:218-224.
4. Volmar KE, Vollmer RT, Jowell PS, Nelson RC, Xie HB. Pancreatic FNA in 1000 cases: a comparison of imaging modalities. Gastrointest Endosc. 2005;61:854-861.
5. Elvin A, Andersson T, Scheibenpflug L, Lindgren PG. Biopsy of the pancreas with a biopsy gun. Radiology. 1990;176:677-679.
6. Gupta S, Ahrar K, Morello FA Jr, Wallace MJ, Hicks ME. Masses in or around the pancreatic head: CT-guided coaxial fine-needle aspiration biopsy with a posterior transcaval approach. Radiology. 2002;222:63-69.
7. Chaya C, Nealon WH, Bhutani MS. EUS or percutaneous CT/US-guided FNA for suspected pancreatic cancer: when tissue is the issue. Gastrointest Endosc. 2006;63:976-978.
8. Brandt KR, Charboneau JW, Stephens DH, Welch TJ, Goellner JR. CT- and US-guided biopsy of the pancreas. Radiology. 1993;187:99-104.