S0977 Outcomes of EUS-Directed Fiducial-Based Image-Guided Radiation Therapy vs Non-Fiducial-Based Image-Guided Radiation Therapy for Esophageal and Pancreatic Cancer

Abstract

INTRODUCTION: Conformal Image Guided Radiotherapy (IGRT) including Stereotactic Body Radiotherapy (SBRT) is often used in the treatment of esophageal and pancreatic cancer. Fiducials are placed via Endoscopic Ultrasound (EUS) for optimal tumor targeting with image guidance. The goal is to deliver radiation targeted to the tumor with fewer side effects than conventional RT. In our study we test this hypothesis by comparing outcomes of patients with esophageal and pancreatic cancer who received EUS-directed fiducial based IGRT vs those who received non-fiducial based IGRT. METHODS: Patients who underwent IGRT for esophageal and pancreatic cancer from January 2016 to March 2020 were reviewed for outcomes. Patients who underwent EUS-directed fiducial placement prior to IGRT were compared to those who did not receive fiducial placement. RESULTS: A total of 114 patients undergoing IGRT met our inclusion criteria with 85 males and 29 females, mean age 66.7 years. There were 39 patients in the fiducial group and 75 in the non-fiducial group. The disease stages were similar for both groups (P = 0.11). There were 74 patients with esophageal cancer and 40 with pancreatic cancer. Nearly half (46.4%) of the patients underwent surgery. Surveillance imaging was reviewed to identify disease recurrence and progression, which was similar for both fiducial (65.7%) and non-fiducial groups (56.1%, P = 0.35). However, during subgroup analysis there was less recurrence in the pancreatic cancer patients who had EUS-directed fiducial placements prior to IGRT (76.5% v 40.0%, P = 0.025) (Table 1). Most of these patients also received high dose SBRTTable 1. There was no difference in mortality (56.4% v 45.3%, P = 0.47) or frequency of metastasis (71.4% v 59.1%, P = 0.22). The rate of adverse events was higher in the non-fiducial group (n = 25) with 5 cases of severe complications resulting in death or inability to complete radiation while there were no severe complications in the fiducial group. However, this difference was not statistically significant (P = 0.1660). CONCLUSION: EUS-directed fiducial placement is beneficial for IGRT in patients with pancreatic cancer as it reduces the risk of disease recurrence due to more precise targeting. There is also a lower rate of complications and side effects due to avoidance of normal tissue which may potentially help patients to complete therapy and improve patient compliance and tolerance.