EUS-Guided Fiducial Placement (EUS FNF) Prior to Targeted Radiation Therapy in Abdominal and Pelvic Tumors: A Case Series

Abstract

Introduction: Stereotactic radiosurgical techniques, such as CyberKnife, and image guided radiation therapy (IGRT) deliver precisely aimed radiation beams to tumors while minimizing radiation to adjacent normal tissue. Internal radiographic markers, or fiducials, serve as reference points to accurately delineate tumors and guide radiation therapy. Published reports describe fiducials placed surgically or percutaneously under US or CT guidance, as well as EUS-guided placement of thoraco-abdominal fiducials, but there have been no reports of gastroenterologists using EUS to guide fiducial placement in the prostate. We describe a case series of EUS-guided placement of fiducials (EUS FNF), which provides not only an alternative to invasive surgical methods, but allows access to structures that may be difficult to reach percutaneously. Methods: Five patients scheduled for CyberKnife or IGRT were evaluated for tumor localization and fiducial placement via EUS. 3 mm × 0.8 mm gold seeds were backloaded into a 19G FNA needle, and a linear array echoendoscope was used to deploy the fiducials into the area of interest under EUS and fluoroscopic guidance. Post-procedure abdominal X-rays or CT scans were performed to confirm fiducial positioning. All patients received intravenous antibiotics prior to EUS FNF and completed up to five days of oral antibiotics following the procedure. Results: A total of sixteen fiducials were used in five patients; one was lost in the stomach during attempted placement. Seven were placed in three abdominal tumors: one pancreatic uncinate adenocarcinoma, one metastatic melanoma in the uncinate process, and one metastatic cholangiocarcinoma in a periduodenal lymph node. Eight gold seeds were deployed in two patients with prostate cancer in four quadrant fashion to delineate the prostate. There was no reported migration of the fiducials at the time of radiation therapy and no complications were noted due to fiducial placement. Conclusions: EUS FNF to facilitate stereotactic radiosurgical and image guided radiation therapy is a new and safe alternative to traditional surgical or percutaneous approaches. In addition to being less invasive, EUS FNF provides the advantage of targeting lesions in difficult, more posterior locations such as the uncinate process. Moreover, we describe the use of a linear array echoendoscope for EUS FNF placement in the prostate, thus adding to the expanding list of indications for EUS.