ESTRO 2025 - Abstract Book

S2885

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

ESTRO 2025

3654

Proffered Paper Thermoradiotherapy optimization and evaluation considering uncertainties in thermal and dielectric tissue properties Timoteo D Herrera 1,2 , Jakob Ödén 3 , Jort Groen 1,2 , Petra Kok 1,2 , Johannes Crezee 1,2 1 Radiation Oncology, Amsterdam UMC, Amsterdam, Netherlands. 2 Cancer biology and immunology, Treatment and quality of life, Cancer Center Amsterdam, Amsterdam, Netherlands. 3 Physics, RaySearch Laboratories AB, Stockholm, Sweden Purpose/Objective: Hyperthermia has a radiosensitizing effect, quantifiable as an enhanced equivalent radiation dose (EQD RT ) using the LQ-model with temperature-dependent parameters. Optimizing radiotherapy with EQD RT objectives has shown to achieve enhanced uniform EQD RT distributions 1 2 . However, uncertainties in thermal and dielectric tissue-properties affect temperature predictions and EQD RT reliability. Robust hyperthermia optimization, incorporating tissue property uncertainty models 3 reduces the chance of needing adjustments due to hotspots (normal tissue temperature exceeding 45°C). This study evaluates EQD RT optimization combined with robust hyperthermia planning, focusing on achieved EQD RT levels and the impact of tissue-property variability. Material/Methods: From a cervical cancer case, we generated 100 hyperthermia patient models, randomly sampling tissue-property distributions. We calculated temperature distributions, selecting only non-hotspot samples for conventional and robust hyperthermia plans computed with Plan2Heat. Using a research version of RayStation 12A, we optimized a conventional radiotherapy plan (23x2 Gy to PTV), and two EQD RT optimized radiotherapy plans (58 Gy EQD RT to GTV), accounting for the temperature distributions of conventional and robust hyperthermia plan (using median tissue property values). We compared achieved EQD RT levels and variation across non-hotspot samples for: conventional radiotherapy alone, conventional radiotherapy with conventional hyperthermia, EQD RT optimized radiotherapy with conventional hyperthermia, and EQD RT optimized radiotherapy with robust hyperthermia. All scenarios assumed five weekly one-hour hyperthermia sessions, with 30-minutes time interval after radiotherapy.