EUS-guided fiducial placement for CyberKnife radiotherapy of mediastinal and abdominal malignancies

Background: The CyberKnife frameless image-guided stereotactic radiosurgery system delivers radiation doses to tumors with high precision by use of real-time image guidance. Radiographic markers (or fiducials) implanted at the tumor site are used as reference points by the system to target the radiation beams. Diagnostic and interventional EUS have multiple applications in the multidisciplinary approach to tumors. Objective: The goal of this prospective study was to evaluate the safety and feasibility of placing fiducials in mediastinal and intra-abdominal tumors under EUS guidance. Design: Patients were evaluated for EUS-guided fiducial placement. A linear echoendoscope was used to localize the tumor, insert a 19-gauge fine needle in the target area, and place the fiducials through the needle lumen. The position of the fiducials was verified by EUS and by fluoroscopy. Setting: Georgetown University Hospital, between February 2005 and August 2005. Patients: Thirteen patients scheduled to undergo CyberKnife radiation therapy. Results: EUS-guided fiducial placement was successful in a total of 11 of 13 patients (84.6%). The locations of the tumors were as follows: retrocrural area at the dome of the diaphragm, porta hepatis, gastroesophageal junction, mediastinum, thoracic paraspinal area, and pancreas. A total of 3 to 6 fiducials were placed in each patient. An infectious complication developed in 1 patient within 30 days of the procedure. Conclusion: EUS-guided fiducial placement in lesions of the mediastinum and abdomen is a feasible and safe technique that can be used to mark a tumor site and guide CyberKnife radiation therapy. This new application of interventional EUS further expands the role of EUS in the multidisciplinary approach to the oncology patient.