ESTRO 2024 - Abstract Book

S4692

Physics - Optimisation, algorithms and applications for ion beam treatment planning

ESTR0 2024

2. Gajewski, J., Garbacz, M., Chang, C. W., Czerska, K., Durante, M., Krah, N., ... & Rucinski, A. (2021). Commissioning of GPU–accelerated Monte Carlo Code FRED for clinical applications in proton therapy. Frontiers in Physics, 8, 567300.

2394

Proffered Paper

Thermoradiotherapy optimization: accounting for thermal enhancement for photon and proton therapy

Jakob Ödén 1 , Brando Pavoni 2

1 RaySearch Laboratories AB, Research, Stockholm, Sweden. 2 Med-Logix Srl, Development, Rome, Italy

Purpose/Objective:

Thermoradiotherapy combines radiotherapy with tumour heating of 39-45°C. This enhances the therapeutic effect through thermal radiosensitization and direct thermal cytotoxicity. Unlike the conventional approach of separately optimizing radiotherapy and hyperthermia plans, our study integrates the thermal effects into a research version of treatment planning system RayStation 12A using the equivalent radiation dose in 2-Gy fractions (EQD2) for the combined treatment.

Material/Methods:

Thermal radiosensitization was modelled voxelwise, assuming an exponential temperature-dependent increase of the LQ-parameters α and β , with an exponentially decreasing exponent with the time interval between corresponding radiotherapy and hyperthermia fractions ( t int ). For a thermoradiotherapy treatment comprising n radiotherapy fraction doses ( d ) and n HT hyperthermia (HT) fractions at temperature T during time t , the EQD2 was calculated as,

where α ( T , t int ) and β ( T , t int ) are the LQ-parameters with hyperthermia, and k ( T ) is the tumour-specific direct thermal cytotoxicity rate. Notably, this equation simplifies to the familiar EQD2 expression for radiotherapy without hyperthermia when n HT =0. In this study, radiobiological thermoradiotherapy optimization was performed for two cases of locally advanced rectum cancer with an integrated boost to the GTV. Bladder, bowel, femoral heads, and spinal cord were considered organs-at-risk (OARs). Heating with the ALBA-4D system was optimized using Plan2Heat aiming for maximum temperature to the target while limiting the normal tissue exposure to 44°C. Subsequently, CT and temperature distribution were imported to the thermoradiotherapy module where robust dual-arc VMAT photon plans (5 mm setup uncertainty) and three-beam pencil beam scanning (PBS) proton plans (5 mm setup uncertainty and 3% range uncertainty) were optimized using two planning strategies: