ESTRO 2025 - Abstract Book

S3499

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

ESTRO 2025

References: 1. Wijsman R et al. Multivariable normal-tissue complication modeling of acute esophageal toxicity in advanced stage non-small cell lung cancer patients treated with intensity-modulated (chemo-)radiotherapy. Rad Onc. . 2015;117(1):49-54. 2. Defraene G et al. Multifactorial risk factors for mortality after chemotherapy and radiotherapy for non-small cell lung cancer. Rad Onc . 2020;152:117-125. 3. Darby SC et al. Risk of Ischemic Heart Disease in Women after Radiotherapy for Breast Cancer. N Engl J Med . 2013;368(11):987-998. 4. Bogowicz M et al. MO-0636 Optimization of adaptive aperture to improve organs at risk sparing in proton therapy. Rad Onc. 2022;170:S567-S568.

2366

Poster Discussion A comprehensive clinical commissioning and first clinical implementation of head and neck discrete proton arc treatments Francesco Fracchiolla 1 , Erik Engwall 2 , Victor Mikhalev 2 , Marco Cianchetti 3 , Irene Giacomelli 3 , Benedetta Siniscalchi 3 , Johan Sundström 2 , Otte Marthin 2 , Viktor Wase 2 , Mattia Bertolini 3 , Roberto Righetto 1 , Annalisa Trianni 1 , Frank Lohr 3,4 , Stefano Lorentini 1 1 UO Fisica Sanitaria, APSS, Trento, Italy. 2 RaySearch, Laboratories AB, Stockholm, Sweden. 3 UO Protonterapia, APSS, Trento, Italy. 4 CISMed, University of Trento, Trento, Italy Purpose/Objective: To perform a complete clinical commissioning of discrete proton arc therapy (PAT) plans for head and neck (H&N) treatments. Material/Methods: 10 H&N cancer patients (median prescription dose 70GyRBE) were selected. Both PAT and MFO were robustly optimized as in our clinical routine. PAT plans were optimized by using 30 angle directions and a final number of 360 energy-layers. Comparisons were performed in terms of: • nominal dose distributions • robustness analysis • NTCP endpoints (xerostomia,swallowing dysfunction, risk of tube feeding and sticky saliva) • LET d • Probability of at least one replanning • Delivery time (both for PAT plans with 30 and 20 directions) Results: In Figure1 a dose comparison between PAT and MFO plans, for one patient, is shown. No statistically significant difference was found in the entire cohort of patients for target coverage (D 95 and D 98 ) and maximum dose to primary OARs (except for brainstem), neither in nominal plans (see Table1) nor in robustness analysis. Brainstem and secondary OARs showed a significant dose reduction in terms of mean dose in the PAT plans. Max LET d distributions in brain structures showed no statistical differences between PAT and MFO plans. Median NTCP was significantly reduced in PAT plans for xerostomia (ΔNTCP=8.5%), while reductions in other endpoints were not significant. The need of at least one replanning during the treatment for PAT was similar to MFO, showing that the established clinical workflow for monitoring of anatomy changes will remain the same for both techniques. Comparison in terms of delivery time gave the following results: • 31 minutes for MFO