923 Endoscopic Ultrasound-Guided Fiducial Placement for Stereotactic Body Radiation Therapy in Patients With Pancreatic Adenocarcinoma

Abstract

INTRODUCTION: Stereotactic body radiotherapy (SBRT) has emerged as a novel therapeutic option in pancreatic cancer care. In the absence of diagnostic quality CT-on-rails or on-board MRI, accurate delivery of SBRT relies on fiducial markers. Endoscopic ultrasound (EUS) has become the preferred method for fiducial markers placement. The aim of this study is to report the technical feasibility and safety of EUS-guided fiducial placement and to evaluate the technical benefit and SBRT outcomes in a cohort of patients with pancreatic cancer (PC). METHODS: A retrospective chart review was performed for all (n = 67) PC patients referred for EUS-guided fiducial placement by a single endosonographer (MSB) at a tertiary cancer center between 2016 and 2019. Data regarding EUS-related technical details and adverse events were recorded. The continuous visibility of the fiducial markers was assessed by an experienced medical physicist on simulation CT and during the final treatment fraction on cone beam CT. RESULTS: During the study period, 67 PC patients underwent placement of 174 fiducial markers under EUS guidance (Table 1). Technical success rate of fiducial placement was 97%. Technical difficulty due to intervening blood vessels was noted in 2 (3%) patients. EUS evaluation showed duodenal invasion in one case and fiducial placement was canceled. All patients received periprocedural antibiotics and no immediate or delayed adverse events were reported. The average time to simulation CT after marker placement was 4.6 days (range, 1-53). 64 (96%) patients received SBRT after fiducial placement (Table 2). Of the total 174 fiducials placed, 165 (95%) fiducial markers were clearly visible on both the CT simulation and cone beam CT scan acquired on the last day of SBRT delivery. 9 (5%) fiducial were not useful for SBRT delivery most likely due to migration or poor visibility. No major SBRT-related toxicity was reported. CONCLUSION: Our results demonstrate that EUS-guided fiducial placement is safe and effective in target volume delineation, facilitating SBRT delivery in PC patients. Further clinical trials are needed to determine the optimal type of fiducial to place under EUS-guidance and the survival benefits in patients with pancreatic cancer.