S2922
RTT- RTT operational practice and workflow innovations
ESTRO 2026
Vickie Kong 1,2 , Peter Chung 1,2 , Jeff Winter 1,2 , Winnie Li 1,2 1 Radiation Medicine Program, Princess Margaret Cancer Centre, Toronto, Canada. 2 Department of Radiation Oncology, University of Toronto, Toronto, Canada Purpose/Objective: Adaptive Radiation Therapy (ART) enhances treatment precision by accounting for anatomical and physiological changes throughout the treatment course. While ART is known to improve clinical outcomes, its implementation is resource-intensive, requiring frequent imaging, plan adaptation, and increased clinical oversight. In contrast, non-adaptive CBCT-guided workflows use static plans but often necessitate reactive interventions that also consume significant time and departmental resources. This study aims to quantify the time-related burden of unplanned activities in non-adaptive workflows and identify disease sites that may benefit most from planned ART, particularly in the context of limited ART- capable devices in Canada. Material/Methods: A retrospective analysis was performed on 6,887 treatment fractions from 300 patients treated with CBCT-guided radiotherapy across 20 treatment techniques of various disease sites. Unplanned activities, such as repeated CBCT acquisitions, aborted sessions, additional planning CTs, and mid-course replanning, were identified through electronic medical records and imaging logs. Time burden was calculated using timestamp data from treatment management systems. The study was approved by the institutional Quality Improvement Review Committee. Results: Repeated CBCTs were required in 55% of patients, resulting in 201.9 hours of additional imaging time. Each repeated CBCT added an average of 13 minutes (range: 2–219 minutes), impacting both patient experience and departmental throughput. Bladder and gynecologic cancers exhibited the highest frequency of repeat imaging, often due to organ filling variability. Six sessions were aborted and rescheduled due to unresolved anatomical discrepancies. Fifteen patients required plan modifications, including 9 repeat planning CTs, and 3 sarcoma cases with treatment interruption of 2-6 days. Conclusion: Non-adaptive CBCT-guided workflows impose a substantial resource burden, often comparable to or exceeding that of ART. These findings support a more strategic implementation of ART, particularly for bladder, cervix, and sarcoma cancers, where anatomical variability frequently disrupts standard
Conclusion: Mid-treatment sCT offers objective dosimetric verification of anatomical changes. Δ CS of ≥ 10 mm may prompt early review, while weight loss is less consistently predictive. sCT-based decision support could reduce both overlooked failures and unnecessary replanning and warrants prospective validation. References: 1. Hay, L. K., Paterson, C., McLoone, P., Miguel- Chumacero, E., Valentine, R., Currie, S., Grose, D., Schipani, S., Wilson, C., Nixon, I., James, A., & Duffton, A. (2020). Analysis of dose using CBCT and synthetic CT during head and neck radiotherapy: A single centre feasibility study. Technical innovations & patient support in radiation oncology, 14, 21–29. https://doi.org/10.1016/j.tipsro.2020.02.004 2. Allen, C., Yeo, A. U., Hardcastle, N., & Franich, R. D. (2023). Evaluating synthetic computed tomography images for adaptive radiotherapy decision making in head and neck cancer. Physics and imaging in radiation oncology, 27, 100478. https://doi.org/10.1016/j.phro.2023.100478 Keywords: Adaptive Radiotherapy, Synthetic CT, Dose Digital Poster 2284 Resource burden in CBCT-Guided Radiotherapy: Identifying Priority Sites for Adaptive Implementation
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