ESTRO 2025 - Abstract Book

S4220

RTT - Education, training, advanced practice and role developments

ESTRO 2025

dosimetric planning. While the feasibility of similar implementations have been discussed and debated in various institutions over the past two decades, this approach seems feasible with some adjustment to scope of work, and concurrent training. Establishing a dedicated unit allows for more freedom in bringing forward scheduled treatment, in part due to a larger proportion of inpatients, and ability to liaise with ROs and coordinate operational schedules directly, benefitting patients who require RT urgently.

Keywords: Palliative, accelerated planning-and-treatment

References: Dennis, K. et al., (2020, November). Rapid Access Palliative Radiotherapy Programmes. Clinical Oncology , 32 (11), 704 - 712. doi:https://doi.org/10.1016/j.clon.2020.08.002 O'Leary C. et al., (22 August, 2023). Palliative Radiotherapy and the Introduction of a Rapid Access Palliative Clinic in a National Radiation Oncology Network. Irish Journal of Medical Science , 193 , 577 - 583. doi:https://doi.org/10.1007/s11845-023-03494-4 Zhao T. et al., (01 November, 2021). Clinical Workflow for Planning and Treating Palliative Patients on Diagnostic Images. International Journal of Radiation Oncology Biology Physics , 111 (3), e496. doi:https://doi.org/10.1016/j.ijrobp.2021.07.1369

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Proffered Paper Feasibility of Therapist-Driven MR-guided adaptive radiotherapy for oligometastatic disease: Geometric accuracy and dosimetric impact Amanda Moreira 1 , Winnie Li 1,2 , Iymad R Mansour 1,2 , Mame Faye 3 , Aruz Mesci 1,2 , Enrique Gutierrez 1,2 , Ali Hosni 1,2 , Patricia Lindsay 1,2 , Peter Chung 1,2 , Jeff D Winter 1,2 1 Radiation Medicine Program, Princess Margaret Cancer Centre, Toronto, Canada. 2 Department of Radiation Oncology, University of Toronto, Toronto, Canada. 3 Radiation Oncology Branch Radiation Oncology, Center for Cancer Research, National Cancer Institute, Bethesda, USA Purpose/Objective: The need for daily, online recontouring by radiation oncologists (RO) is a major limitation in most MRI-guided adaptive radiation therapy (ART) applications due to the associated human resource implications. This has been overcome for prostate ART via successful implementation of radiation therapist (RTT) led workflows. With increasing utilization of MR-guided adaptive stereotactic body radiation therapy (SBRT) in oligometastatic disease, we evaluated a potential RTT-led workflow by comparing geometric accuracy and dosimetric uncertainty between RO and RTT recontouring. Material/Methods: Eight patients with oligometastatic disease (soft tissue and bone metastasis) were retrospectively investigated. For each patient, five RTTs and five ROs recontoured all target and organ-at-risk (OAR) volumes within a 2 cm ring of the target. Consensus RO contours were generated for targets and OARs via the Simultaneous Truth and Performance Level Estimation (STAPLE) method and geometric accuracy was evaluated for each RTT and each RO contour versus the RO-STAPLE contour using Dice similarity coefficient (DICE) and Hausdorff mean distance to agreement (MDA). Additionally, a RO qualitatively scored all contours blinded to profession using a 5-point Likert scale. Lastly, dosimetric impact of RO versus RTT contour differences from the RO-STAPLE were assessed by extracting dose volume histogram (DVH) metrics from the clinically delivered adaptive plan, including PTV D95 and D0.5cc for OARs. The Wilcoxon signed rank test compared DICE and DVH metric differences between RTT and RO contours.

Results: Mean and standard deviation DICE coefficients for GTV targets were 0.82±0.06 for RTTs and 0.85±0.09 (p < 0.05) for