S1714
Physics - Dose prediction/calculation, optimisation and applications for particle therapy planning
ESTRO 2026
neuroanatomical changes over five years in children treated with PBRT for craniopharyngioma. These findings highlight the need for careful treatment planning to minimize long-term neuroanatomical alterations and their potential impact on pediatric brain tumor survivors. References: 1.Rashid A, et al. A prospective study of corpus callosum regional volumes and neurocognitive outcomes following cranial radiation for pediatric brain tumors. Childs Nerv Syst 2017.2.Souris K, et al. Fast multipurpose Monte Carlo simulation for proton therapy. Med Phys 2016.3.Fischl B. FreeSurfer. Neuroimage 2012. Keywords: Proton treatment, LETd Retrospective study of the combined effect of dose and dose-averaged LET on local tumour control in adenoid cystic carcinoma treated with carbon ions Vittoria Pavanello 1,2 , Giuseppe Magro 1 , Stefania Russo 1 , Maria Bonora 3 , Sara Ronchi 3 , Santa Gabriella Bonaccorsi 1 , Beatrice Amaglio 1 , Anna Maria Camarda 3 , Rossana Ingargiola 3 , Barbara Vischioni 3 , Ester Orlandi 3,4 , Silvia Molinelli 1 Poster Discussion 1250 1 Medical Physics, National Center for Oncological Hadrontherapy, Pavia, Italy. 2 Physics, IUSS - School for Advanced Studies, Pavia, Italy. 3 Radiation Oncology, National Center for Oncological Hadrontherapy, Pavia, Italy. 4 Clinical, Surgical, Diagnostic and Pediatric Sciences, University of Pavia, Pavia, Italy Purpose/Objective: To investigate the association between relative biological effectiveness (RBE) modeling, delivered RBE- weighted dose (DRBE), dose-averaged LET (LETd) distributions, and local tumor control (LC) in adenoid cystic carcinoma (ACC) patients treated with carbon- ion radiotherapy (CIRT). Material/Methods: 78 ACC patients treated with CIRT between 2016 and 2023 were retrospectively analysed (median follow-up: 47 months; range: 7–101). Treatment was planned using the LEM I model [1], with prescriptions of 65.6 or 68.8 Gy(RBE) in 16 fractions. 25 patients who developed local recurrence were classified as the progressive disease (PD) group, while the remaining constituted the LC cohort.Univariable/multivariable logistic regressions assessed clinical predictors (age, gender, clinical stage, GTV) of recurrence ( α =0.05). For each patient, DRBE distributions were re-calculated using the LEM-I model (DLEM) and the mMKM model (DMKM) [1]. Clinical target volume (CTV) DVHs were generated for both models and stratified by prescription level. LETd distributions were combined
Larger tumor volume correlated with reductions in both the right pallidum ( β = -0.39, p = 0.020) and amygdala ( β = -0.38, p = 0.013). Patients with left hippocampal shrinkage had higher left lateral field doses (median: 12.9 Gy, p = 0.011), lower LETd (median: 2.20 keV/µm, p = 0.036), and higher right lateral field LETd (median: 5.69 keV/µm, p = 0.042) and dose (median: 4.77 Gy, p = 0.022) (Figure 1). Multivariable regression identified higher ipsilateral dose and contralateral LETd as predictors of five-year shrinkage of the left hippocampus and left pallidum, respectively (Table 1).
Conclusion: This study demonstrates that both physical dose and LETd in targeted brain regions significantly influence
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