S2169
Physics - Inter-fraction motion management and daily adaptive radiotherapy
ESTRO 2026
beam CT-images in RayStation (v2024A DTK, RaySearch Laboratories, Sweden), a dosimetric analysis was performed for the first LoP-patient and an adaptive Radixact (Accuray Inc., USA) treatment was simulated. Results: Between November-2024 and Novmber-2025, 33 LACC-patients were included, and 7 were referred to LoP-treatment. One LoP-patient was excluded due to confidentiality. Prescribed dose was 50.4Gy/28 fractions, delivered using volumetric modulated arc therapy on a TrueBeam-accelerator (Varian Medical Systems, USA). Median(range) PTV-volume was 658cc(269-1521) for non-LoP treatments, and 617cc(311-779), 582cc(376-773) and 725cc(412-851) for LoP dorsal-, ventral- and total-treatments, respectively.
rectal filling and patient-specific factors. Daily CBCT enables accurate motion quantification and supports anisotropic margin design. Incorporating these findings into adaptive planning helps preserve tumour control probability (TCP) while minimising normal tissue complication probability (NTCP), optimising the therapeutic ratio. Keywords: Inter-fraction displacement, Adaptive Radiotherapy Implementing Cone-Beam CT-based library of plans treatment for locally advanced cervical cancer – first-year clinical experience Hedda Enocson 1,2 , Lotta Lundgren 1 , Charlotte Thornberg 1 , Elinore Wieslander 1 , Victor Pham 1 , Per Munck af Rosenschöld 1,2 , Maria Bjurberg 3 , Emilia Persson 1,4 1 Radiation Physics, Department of Hematology, Oncology, Radiation Physics, Skåne University Hospital, Lund, Sweden. 2 Medical Radiation Physics, Lund University, Lund, Sweden. 3 Oncology, Digital Poster 3863 Department of Hematology, Oncology, Radiation Physics, Skåne University Hospital, Lund, Sweden. 4 Medical Radiation Physics, Department of Translational Medicine, Lund University, Malmö, Sweden
The LoP total-treatment resulted in 17% (dorsal, p<0.001, paired t-test) and 25%
(ventral, p=0.002, paired t-test) larger median PTV- volumes.All LoP-patients required use of both ventral- and dorsal-plans. The total-plan was required for 4 patients, selected in total of 10 fractions (Fig.1A). Mean(SD) image review time was 5.6min(1.9) and 3.8min(1.7) for LoP- and non-LoP-patients respectively (Fig.1B). For the first LoP-patient, dose analysis showed that D98%,CTV was >95% of the prescribed dose for all but one fraction (Fig.2).
Purpose/Objective: Motivated by reduced side effects, adaptive
treatments for locally advanced cervical cancer (LACC) are increasingly being integrated into clinical routine. Here, we present our first-year clinical experience implementing a library of plans-treatment (LoP) for LACC on a cone-beam CT-linac. Material/Methods: Since November 2024, all LACC-patients referred to radiotherapy at our centre have been considered for LoP-treatment. In this work, we retrospectively reviewed the first year following the clinical introduction of LoP. Using PET-CT (empty bladder) and CT (comfortable bladder) images, patients were classified as LoP- and non-LoP based on the variation in uterus position. For LoP-patients (uterus variation >2-3cm), three target volumes and corresponding treatment plans were created for dorsal-, ventral- and total-target (dorsal+ventral) using a 1cm CTV-to-PTV margin. During each treatment fraction, the plan that best suited the daily anatomy was selected based on online-image review. Non-LoP-patients were referred to single-plan ITV-treatment with a 5mm ITV-to-PTV margin.PTV-volumes and online image review time (time between imaging and beam-on) were analysed for all patients. A treatment plan selection analysis was performed for LoP-patients. Using corrected cone-
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