S2982
Invited Speaker
ESTRO 2026
5257 Photons: CBCT and MR imaging enabled online- adaptive radiotherapy Daniela Thorwarth Section for Biomedical Physics, Department of Radiation Oncology, University Hospital Tübingen, Tübingen, Germany Recent developments in the field of on-board imaging and software technology have enabled the clinical implementation of online adaptive radiotherapy using photons based on cone-beam computed tomography (CBCT) and magnetic resonance (MR) imaging. Both on-board imaging techniques, CBCT and MR imaging, allow for online adaptation of the radiotherapy plan based on the daily anatomy including image post-processing, automatic contouring, online replanning and secondary dose checks. In this presentation, recent advances in CBCT- and MR- guided online adaptive photon radiotherapy will be discussed. Furthermore, novel artificial intelligence and deep learning approaches have been proposed for potential realization of real-time adaptive radiotherapy in the near future. In addition, new techniques for fast 3D imaging acquisition will be summarized as well as opportunities for biological adaptation and potential directions for cross- fertilization of online adaptive photon and proton radiotherapy. 5259 RTT perspective: Making BgRT work in daily practice Mairead Daly Division of Cancer Sciences, University of Manchester, Manchester, United Kingdom Biologically-guided radiotherapy (BgRT) represents one of the most compelling advances in modern radiation oncology: the prospect of treatment adapted not just to anatomy, but to tumour biology and functional response in real time. However, the distance between that prospect and consistent clinical delivery remains significant. This talk examines that translational gap through a therapeutic radiographer/radiation therapist (RTT) lens, with particular attention to the practical, workflow, and implementation dimensions that determine whether BgRT becomes embedded in daily practice or remains a capability in waiting. Some bottlenecks represent necessary caution; however, others are structural barriers delaying adoption without corresponding benefit. Distinguishing between the types of bottlenecks is
essential if BgRT development and implementation is to move forward deliberately and effectively. Three translational challenges sit at the heart of implementing BgRT. First, biological validation: the clinical actionability of biological signals, such as imaging biomarkers, functional parameters, or treatment response indicators, remains incompletely established. RTTs are increasingly expected to act on these signals within adaptive workflows, yet the evidence base underpinning when, and how to do so is still maturing. Second, technical validation: the tools required to execute BgRT - advanced imaging, artificial intelligence (AI)-assisted planning, online adaptive platforms - carry their own uncertainty. Robust quality assurance (QA) frameworks and clear validation standards are prerequisites for clinical confidence, and their absence places disproportionate burden on the RTT workforce. Third, standardisation across centres: without harmonised protocols, shared definitions of biological signal, and consistent implementation infrastructure, BgRT risks becoming a capability that is implemented unequally rather than at scale. Variation across departments introduces inequity in both access and quality. Addressing these challenges requires equal attention to people, process, and technology. Structured training pathways, genuine role clarity, and decision- making authority within multidisciplinary team (MDT) frameworks are required. Furthermore, workflows must be redesigned, not simply extended, to absorb demands of BgRT. 5262 Medical physics: Biomarkers Faisal Mahmood Oncology, Odense University Hospital, Odense, Denmark Biologically guided radiotherapy (RT) holds the promise of moving beyond anatomically defined treatment towards individualized dose delivery based on tumour biology. Central to this vision is the use of biomarkers to inform patient selection, target definition, and treatment adaptation. However, despite extensive research, the integration of biomarkers into routine clinical decision-making remains limited. This presentation will focus on the role of biomarkers as a potential bottleneck in translating biologically guided RT into clinical practice. Key concepts and definitions of prognostic and predictive biomarkers will be introduced, with emphasis on imaging biomarkers that can be acquired within existing RT workflows. Examples of promising and clinically feasible biomarkers, including diffusion MRI-derived
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