ESTRO 2025 - Abstract Book

S2770

Physics - Dose prediction, optimisation and applications of photon and electron planning

ESTRO 2025

References: Giebeler, A., Newhauser, W.D., Amos, R.A. et al. Standardized treatment planning methodology for passively scattered proton craniospinal irradiation. Radiat Oncol 8, 32 (2013). Zhou Y, Ai Y, Han C, Zheng X, et al. Impact of setup errors on multi-isocenter volumetric modulated arc therapy for craniospinal irradiation. J Appl Clin Med Phys. 21, 11 (2020). Cindy lm, Zhe Lu, Sogol M, et al. Development and validation of age-specific risk prediction models for primary ovarian insufficiency in long-term survivors of childhood cancer: a report from the Childhood Cancer Survivor Study and St Jude Lifetime Cohort. Lancet Oncol. 24, 12 (2023).

1488

Poster Discussion Clinically Meaningful Improvements to Breast Radiotherapy: A Blinded Evaluation of a new Hybrid VMAT/IMRT Technique featuring Dynamic Collimation Ben Archibald-Heeren 1 , John Boyages 2 , Miriam Boxer 3 , Huong Nguyen 4 , Pinky Tiu 4 , Fiona Gordon 5 , Nathan Mauro 4 , Ashley Harwood 4 , Trent Aland 6 1 Development and Implementation, Icon Cancer Centres, Sydney, Australia. 2 Icon Wahroonga, Icon Cancer Centres Wahroonga, Sydney, Australia. 3 Icon Concord, Icon Cancer Centres, Sydney, Australia. 4 Icon Plan, Icon Cancer Centres, Brisbane, Australia. 5 Icon Wahroonga, Icon Cancer Centres, Sydney, Australia. 6 Icon Core, Icon Cancer Centres, Brisbane, Australia Purpose/Objective: RapidArc Dynamic (RAD) is a new commercial optimization and delivery system that enables the addition of dynamic collimator rotation and integrated static angle modulated ports (STAMPs) within volumetric arc modulated therapy (VMAT). Initial research has shown the potential for improvements in breast radiotherapy clinical goal metrics 1 . This study is the first systematic blind study of clinical reviews of plans generated by RAD in comparison to current VMAT plans. Material/Methods: Ten breast plans were retrospectively planned with both a VMAT technique and the new RAD algorithm. Plans were optimized twice by a dosimetrist in a Varian Eclipse V18.1 treatment planning system with known reference clinically accepted distributions. Dosimetrists were instructed to improve beyond the clinical plan by optimizing to minimize organ doses whilst maintaining target coverage. In each case the achieved plan quality of the opposing plan was unknown and total optimization time was recorded. The final dose distribution and clinical metrics were reviewed by two radiation oncologists and five dosimetrists from three clinics. Reviews were blinded from the planning methodology. For each case the reviewer scored plan preferences (plan 1, plan 2 or equivalent) on target goals, organ goals and dose distributions based on their clinical judgement of a meaningful improvement. Results: Of the 70 review sessions performed across 7 clinical experts the rapid arc dynamic plan was chosen as preferred in 63 (90%) reviews. The remaining 7 case were determined to be equivalent in plan dosimetry. In no case was VMAT preferred.