Breath Hold Upper Abdominal Stereotactic Body Radiotherapy (SBRT) with Surface Guidance: Single Center Experience

Abstract

Surface tracking systems which is integrated to SBRT treatments enables motion tracking with 3D camera technology. We aim to evaluate treatment related outcomes in breath hold upper abdominal SBRT with surface guidance. Patients with upper abdominal lesions treated with breath hold and SGRT were evaluated retrospectively. Half an hour coaching was given to each patient prior to simulation. The CT scans were performed with IV contrast mostly in end insprium or end exprium phases whichever more comfortable and reproducible. The planning CTs were fused with magnetic resonance images (MRI) and positron emission CTs (PET-CT). Target and critical structures were contoured. All treatments were done in Varian EDGE (Varian, Palo Alto, CA, USA). Patients were navigated both with verbal guidance and tracking screen. Cone beam CTs (CBCT) were acquired with breath hold before treatment and 6D couch corrections were done. Optical Surface Management System (OSMS; Varian, Palo Alto, CA, USA) was used both in setup and motion tracking. Automated beam hold control was used during the treatment when patients moved outside of pre-defined range. Treatment duration varied depending on patient’s breath hold performance, prescribed dose, field number and modulation. Local recurrence is defined as size increase in MRI or increase in uptake in PET-CT. Fifty lesions were treated between May 2017 and July 2019. There are 33 liver metastases, 10 pancreatic tumors, 4 primary liver tumors and 3 paraaortic lymph node metastases. Thirty-eight patients have regular follow ups. Median follow up is 9 months. The doses are 25-60 Gy in 3-5 fractions. Ten patients experienced local failure. Local control rates for liver metastases, pancreatic tumors and hepatocellular carcinoma 85%, 60% and 66% respectively. Gastric bleeding is observed in one patient who has a pancreatic tail tumor after 1 year of treatment. It is possible to reduce respiratory organ motion with breath hold in SBRT treatments. SGRT is a noninvasive, real time method without using ionized radiation and allow us to make a correct setup and intra fractional monitoring.