Objective: Image-guided radiation therapy allows precise tumor targeting using real-time tracking of radiopaque fiducial markers. To enable appropriate tracking, it is recommended to place fiducials with "ideal fiducial geometry" (IFG). Our objectives were to determine the proportion of patients in whom IFG can be achieved when fiducials are placed by endoscopic ultrasound (EUS) and surgery and to determine if attaining IFG is necessary for delivering radiation.
Methods: This single-center retrospective cohort study included 77 patients with biopsy-proven advanced pancreatic cancer who underwent either EUS-guided or laparotomy/laparoscopy-assisted fiducial placement between September 2005 and July 2009.
Results: Gold fiducials were implanted by EUS in 39 patients (51%) and by surgery in 38 patients (49%). The proportion of patients with IFG was significantly higher for surgical placement [18/38, 47%; 95% confidence interval (CI), 32%-63%] compared with EUS-guided placement (7/39, 18%; 95% CI, 8%-32%), P = 0.0011. However, fiducial tracking was successfully used for Cyberknife therapy in 35 (90%) of 39 (95% CI, 77%-97%) patients in the EUS group compared with 31 (82%) of 38 (95% CI, 67%-92%) patients in the surgery group. There were 5 procedure-related complications in the EUS group.
Conclusions: Achieving IFG appears unnecessary for successful tracking and delivery of radiation.