ESTRO 2025 - Abstract Book

S12

Invited Speaker

ESTRO 2025

order to expedite treatment for our sickest patients. Substantial data has emerged in the last few years demonstrating that direct to unit paradigms are feasible and may increase the speed with which patients are able to be treated in radiation oncology. Herein we will discuss the basics of palliative direct to unit radiotherapy including a general workflow and case based discussion as well as some of the relevant data supporting this novel treatment paradigm.

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Speaker Abstracts Simulation-free radiation therapy: Clinical consideration Eva Versteijne Radiation Oncology, AmsterdamUMC, Amsterdam, Netherlands

Abstract: As radiation oncology evolves toward more patient-centered and efficient treatment paradigms, adaptive radiotherapy—particularly in a simulation-free context—is emerging as a promising strategy to streamline care and improve outcomes. This presentation will explore the rationale, clinical workflow, and early outcomes associated with simulation-free radiation therapy (SFRT) within adaptive treatment frameworks, highlighting its clinical relevance, implementation, and future directions. Patient cases will be presented to illustrate the impact on treatment timelines, patient experience, and operational logistics. Simulation-free radiotherapy eliminates the need for a dedicated planning CT by using existing diagnostic imaging (such as diagnostic CT or MRI) or on-board imaging modalities like cone-beam CT (CBCT) for both treatment planning and delivery. This approach is particularly valuable when rapid treatment initiation is critical, and has already been applied in select indications—most notably palliative radiotherapy and early feasibility studies in stereotactic and curative settings. By omitting the conventional simulation step, SFRT offers several advantages: faster time-to-treatment, reduced burden on patients (especially the frail or ill), and increased workflow efficiency. When combined with adaptive techniques, SFRT allows daily anatomical changes to be incorporated into the treatment plan, enabling improved target coverage and sparing of healthy tissue. Clinical experience suggests that SFRT, integrated within an adaptive framework, can maintain or even enhance dosimetric accuracy. Looking ahead, SFRT holds significant potential to support rapid and adaptive radiotherapy, particularly when integrated with emerging technologies such as AI-driven organ-at-risk delineation and automated planning systems. Broader adoption will depend on developing standardized protocols and multi-institutional collaboration to validate and harmonize outcomes across centers. This talk will provide clinicians, physicists, and researchers with a practical and forward-looking perspective on simulation-free adaptive radiotherapy—demonstrating not only that it is feasible, but that it may become a cornerstone of next-generation radiation oncology practice.

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Speaker Abstracts Simulation-free radiation therapy: Physics consideration Alex T Price Radiation Oncology, University Hospitals, Cleveland, USA. School of Medicine, Case Western Reserve University, Cleveland, USA