EUS-Guided Fiducial Placement for Stereotactic Radiosurgery in Pancreatic Cancer

Abstract

Background: Stereotactic radiosurgery (SRS) allows the delivery of a single therapeutic dose of radiation with pinpoint accuracy to solid tumors throughout the body. Implantable radiographic markers (fiducials) are required to enable real-time tracking for targets that move with respiration. Traditionally, these have been placed either surgically or percutaneously using US or CT guidance. Recently, EUS-guided placement has been reported in both thoracic and upper gastrointestinal malignancies. We report our experience with EUS-guided fiducial placement for SRS in pancreatic cancer. Aims: 1. To assess the safety and efficacy of EUS-guided fiducial placement for SRS in pancreatic cancer. 2. To determine if SRS was successfully delivered after EUS-guided placement. Methods and Patients: 16 consecutive patients (12 males, mean age 74) with either unresectable or recurrent pancreatic cancer underwent EUS for fiducial placement over a one year period. After withdrawing the stylet of a 19-g EUS needle 7-8 mm, a gold seed (5.0 × 0.8 mm) was back-loaded into the needle tip and sealed in place with sterile bone wax. The needle could then be passed down the operating channel of the echoendoscope without losing the fiducial. Upon needle insertion into the target lesion, the fiducial was deployed by advancing the stylet. Fluoroscopic guidance was not used. The placement of 2 fiducials at least 2 cm apart was attempted in all patients. Abdominal xray was performed afterward to document placement. An intravenous prophylactic antibiotic was administered in all patients followed by a five day oral course. Results: Fiducials were successfully placed in 14/16 patients; 2 were placed in 13 patients, and only 1 was placed in another patient due to difficult positioning in post-surgical anatomy. Two placement failures occurred due to inability to image tumor recurrence in the surgical bed of Whipple resections. There were no complications related to the EUS procedure or fiducial placement. SRS was successfully performed in the 14 patients using the Cyberknife® robotic radiosurgery system (Accuray, Sunnyvale, CA). One patient required the placement of a third fiducial, as initial tracking failed given a inability to differentiate the original two fiducials. The patient who only had one fiducial initially placed underwent percutaneous placement of a second fiducial to allow SRS. Conclusion: EUS-guided fiducial placement is feasible and safe in pancreatic cancer. Placement of two appropriately spaced fiducials under EUS guidance alone appears adequate to guide successful SRS. Fiducial placement failures result from altered surgical anatomy.