Author: Neal Andruska, Lianna D. DiMaso-Myers 👨🔬
Affiliation: Northwestern Medicine 🌍
Purpose: To provide details on how our clinic assesses respiratory motion during treatment of a pancreatic adenocarcinoma during dose escalated radiation therapy on a linear accelerator with the aid of fluoroscopy and CBCT in a high-volume clinic.
Methods: At our institution, patients selected for dose-escalated radiation therapy of pancreatic adenocarcinoma are treated on a Varian 3.0 TrueBeam LINAC. The patient must have favorable internal anatomy and a stent abutting tumor to be eligible for treatment. Prior to planning, a 4DCT with and without compression are acquired to assess target and OAR respiratory movement. During planning, target delineation, stent movement, and OAR structures are defined using the objectives and constraints listed in Eugen et al. as guidance. The image guidance used prior to treatment includes a CBCT and fluoroscopy to assess patient alignment and respiratory motion. OAR, PRV, and target contours on the DRR and reference CT are used to assess stent movement and assure OARs remain outside of the high-dose region to prevent GI toxicities.
Results: Several patients have been treated with dose-escalated RT to the pancreas at our institution with pre-treatment CBCT and fluoroscopy. Fluoroscopy source direction and assessment, CBCT assessment, contour assessment, and treatment time have all been standardized to assure a short treatment time slot and accurate treatment in our high-volume clinic. Current follow ups show no bowel toxicity symptoms assuring an accurate assessment of bowel and stomach movement.
Conclusion: Dose-escalated RT for pancreatic adenocarcinoma has been safely delivered at our clinic using a LINAC without gating and with and without compression. Our procedure and IGRT assessment give confidence that we can mitigate GI toxicities while maintaining high dose levels to pancreas tumors.