S2357
Physics - Quality assurance and auditing
ESTRO 2026
reductions occurred in the oral cavity ( − 5%, 1.7 Gy) and buccal mucosa ( − 6%, 1.3 Gy). Dose evolution was gradual and continuous, suggesting that improvements stemmed from iterative optimization rather than discrete procedural changes. Importantly, the introduction of new substructures in 2016 did not increase doses to previously defined OOIs, demonstrating that enhanced anatomical precision did not compromise dose sparing. Trends were consistent across diagnostic sub-sites.
Mini-Oral 2129
A Decade of Dose Reduction in Head and Neck Radiotherapy: Temporal Trends in Organ-at-Risk Sparing Anne Ivalu Sander Holm 1 , Maiken Mondrup Hjelt 2 , Emil Rønn 1 , Tine Bisballe Nyeng 1 , Hanne Primdahl 1 , Christian Nicolaj Andreassen 1 , Kasper Toustrup 1 , Line Meinertz Hybel Schack 1 , Jesper Grau Eriksen 1 1 Department of Oncology, Aarhus University Hospital, Aarhus, Denmark. 2 Experimental Clinical Oncology, Aarhus University Hospital, Aarhus, Denmark
Purpose/Objective: Variations in dose–volume histogram (DVH)
parameters over time can reflect evolving treatment planning, contouring practices, and technological advances, potentially influencing clinical outcomes. Long-term DVH monitoring enables assessment of treatment consistency and supports continuous quality improvement in radiotherapy. This study evaluated temporal trends in dosimetrically relevant DVH parameters for all head and neck cancer (HNC) patients treated at a single institution between 2013 and 2023—a period marked by progressive upgrades in accelerator systems, optimization algorithms, and contouring guidelines. Notably, the 2016 implementation of new head and neck contouring standards introduced additional swallowing-related structures, subdividing the larynx and adding the pharyngeal constrictor muscles (PCMs). Material/Methods: A total of 1,521 HNC patients receiving curative-intent radiotherapy from 2013–2023 were analyzed. All organs of interest (OOI) were re-segmented using clinically deployed AI-based models, and relevant DVH parameters were extracted. Annual comparisons were conducted for the glottic and supraglottic larynx (combined as Larynx Total), oral cavity, buccal mucosa, and superior, middle, and inferior pharyngeal constrictor muscles (PCM Total), left and right parotid glands (Parotid Total), left and right submandibular glands (Submandibular Total), and the thyroid gland. The mean dose to principal swallowing and salivary structures was tracked over time and stratified by major diagnostic subgroups to evaluate temporal trends in dose distribution and potential site-specific differences. Results: Across the 10-year period, mean OOI doses decreased consistently, indicating steady improvement in treatment planning and delivery. The greatest dose reductions were observed for the esophagus ( − 37%, 10.0 Gy), larynx ( − 31%, 15.2 Gy), and thyroid ( − 23%, 9.0 Gy). Moderate decreases were seen in the PCMs ( − 19%, 9.1 Gy), parotids ( − 21%, 5.5 Gy), and submandibular glands ( − 14%, 6.8 Gy), while smaller
Conclusion: Over the past decade, mean doses to organs in head and neck radiotherapy steadily decreased at our institution, reflecting ongoing improvements in planning and technology. Reductions were consistent across organs and sub-sites, indicating general institutional optimization rather than site-specific interventions. These findings underscore the value of long-term DVH monitoring for quality assurance and
continual clinical refinement. Keywords: Dose monitoring
Poster Discussion 2150 Radiotherapy QA of hippocampus and hypothalamus contouring for the APPROACH trial (ISRCTN:1339049) Jennifer Golten 1,2 , Emiliano Spezi 3,4 , Anna Bruce 5,6 , Daniel Egleston 5,6 , Elizabeth Miles 6,7 , James Powell 1,2 , Louise Murray 8,9 1 Clinical Oncology, Velindre University NHS Trust, Cardiff, United Kingdom. 2 School of Medicine, Cardiff University, Cardiff, United Kingdom. 3 School of Engineering, Cardiff University, Cardiff, United Kingdom. 4 Medical Physics, Velindre University NHS Trust, Cardiff, United Kingdom. 5 Medical Physics, Clatterbridge Cancer Centre, Liverpool, United Kingdom. 6 National RTQA, National Radiotherapy Trials Quality Assurance (RTTQA) Group, London, United Kingdom. 7 Medical Physics, Mount Vernon
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