Fiducial Placement for Stereotactic Radiation Using Endoscopic Ultrasound: Feasibility Using a Marker Compatible with a Standard 22 Gauge FNA Needle

Background: Stereotactic radiation using fiducial markers permits higher doses of radiation while reducing the exposure of uninvolved, adjacent structures. Endoscopic ultrasound (EUS) has been used to deploy fiducials, although a 19 gauge needle has traditionally been required. In lesions that are distant from the ultrasound probe or require a significant amount of torque to visualize, a 19 gauge needle can be cumbersome. Objective: To report the feasibility of deploying a fiducial compatible with a 22 gauge needle under EUS guidance. Methods: We performed a case series of all patients referred for EUS-guided placement of a fiducial between January, 2006 and November, 2008. Standard practice at our institution is to use a 10 mm × 0.35 mm gold fiducial marker (Visicoil™, IBA Dosimetry USA, Bartlett, TN) that is compatible with a standard 22 gauge EUS fine needle aspiration needle (FNA) (Wilson-Cook, Bloomington, IN) . After the needle is directed into the target, the stylet is removed and the fiducial is inserted into the hollow needle. The stylet is then reinserted to advance the fiducial to the tip of the needle. To avoid coiling, the needle is then withdrawn 10 mm, leaving the fiducial deployed within the target. Medical records were abstracted to identify the location of primary malignancy, location and size of metastatic target for fiducial placement, and subsequent response to stereotactic therapy. Results: Six patients were identified in the endoscopic database with the following primary cancers & targeted metastases: two pancreatic adenocarcinoma (1 celiac and 1 periaortic lymph node), non-small cell lung (left adrenal), cholangiocarcinoma (perihilar lymph node), renal cell (subdiaphragmatic lymph node), and hepatocellular carcinoma (pancreatic tail). Targeted lesions measured 23 ± 14 mm (range 8-45) × 17 ± 8 mm (range 6-27). All fiducials were successfully deployed, 5 using a transgastric and 1 using a transduodenal approach. There were no EUS-associated complications. One patient did not proceed to radiation therapy as a result of interval peritoneal metastasis. However, all fiducials were visible on roentogram. 3 of 5 patients demonstrated radiographic response or resolution to stereotactic therapy, while 2 patients are currently undergoing treatment. Conclusion: To our knowledge, this is the first report using EUS to deploy fiducials that are compatible with a standard 22 gauge FNA needle. This approach is technically feasible and may permit greater access compared to the 19 gauge technique. A prospective trial comparing the technical success and complication rates of the two approaches is warranted.