3452 - Simulation-Free Single-Fraction Conventional and Stereotactic Radiotherapy for Bone and Soft Tissue Metastases
Presenter(s)
J. Javor1, C. J. Tsai2, A. Mesci3, B. J. Cummings4, P. Wong5, B. A. Millar5, R. K. Wong6, L. A. Dawson4, R. Chelvarajah2, A. Agrawal7, K. Del poso-Lee1, N. Wattakiyanon8, T. Tadic4, and E. Taylor5; 1Princess Margaret Cancer Centre, University Health Network, Toronto, ON, Canada, 2Princess Margaret Cancer Centre, Toronto, ON, Canada, 3Radiation Medicine Program, Princess Margaret Cancer Centre, Toronto, ON, Canada, 4Radiation Medicine Program, Princess Margaret Cancer Centre, University Health Network, Toronto, ON, Canada, 5Department of Radiation Oncology, University of Toronto, Toronto, ON, Canada, 6Department of Radiation Oncology, Princess Margaret Cancer Centre, University of Toronto, Toronto, ON, Canada, 7Navodaya Cancer Hospital, Bhopal, Madhya Pradesh, India, 8Ramathibodi Hospital, Bangkok, Thailand
Purpose/Objective(s):
This study explores the feasibility and efficiency of a simulation-free, single-fraction radiation treatment (RT), including stereotactic body radiotherapy (SBRT) for predominantly non-spine bone or soft tissue metastases using recent diagnostic CT (dCT) scans for treatment planning. Single-fraction SBRT has demonstrated superior pain relief compared to conventional multi-fraction radiotherapy, but treatment delays due to simulation CTs remain a challenge. Utilizing dCT images streamlines the workflow, reducing in-hospital wait time for patients.Materials/Methods:
During the preclinical planning phase, development and validation of the workflow was completed. Clinical implementation involved importing dCTs performed within the previous 30 days into the planning system, contouring Clinical Target Volumes (CTVs) and isotropically expanding them by 5-10 mm to generate Planning Target Volumes (PTVs). Additional contours were created to check CT number accuracy and geometric integrity. Prescribed dose ranged from 8-20Gy in 1 fraction and Volumetric Modulated Arc Therapy (VMAT), Intensity Modulated Radiation Therapy (IMRT) or field-based techniques were accepted. Each plan had standard in-house physics quality control checks performed. Time in room and number of cone beam CTs (CBCTs) were recorded. Actual target volume coverage and OAR doses were retrospectively compared with planned metrics using dose accumulation and compared using descriptive analyses.Results:
A total of 40 lesions were treated with simulation-free RT from December 2023 to February 2025. Sites include pelvis (n=14), hip/upper femur (n=2), sternum (n=2), scapula (n=3), lower extremity (n=1), upper extremity (n=3), soft tissue (n=7), rib (n=4), spine (n=4). Most patients (n=30, 75%) received 8-10 Gy in 1 fraction, 10 patients received > 10Gy (range 12-20 Gy). Using CBCT-based dose reconstruction, PTV D95% and CTV D99% were within 8% (range -7.1% to -1.8%; mean: -3%) and 5% (range: -5% to 3.6%; mean: -1%) of planned values, respectively. Maximum dose to critical organs-at-risk was not significantly different compared with planned dose and expected normal tissue tolerances were not exceeded. Average in-room time was 39 minutes (range: 30-57 minutes), which was more than 6 times faster than the average in-hospital wait time for same day field-based treatments (mean 239 mins; std dev 2.4 mins) and 5.8 days faster than the conventional SBRT workflow duration from simulation to treatment delivery. No patient needed a conventional simulation. The maximum number of CBCTs was 4.Conclusion: Utilizing dCT for single fraction conventional RT or SBRT is feasible and efficient, reducing the time patients spend in the department. Future work includes collecting patient reported outcomes, and patient and staff satisfaction with this new process.