Linear energy transfer-inclusive models of brainstem necrosis following proton therapy of paediatric ependymoma

Background and PurposeRadiation-induced brainstem necrosis after proton therapy is a severe toxicity with potential association to uncertainties in the relative biological effectiveness (RBE). A constant RBE of 1.1 assumed clinically, but known vary linear energy transfer (LET). LET-inclusive predictive models may therefore be beneficial during treatment planning. Hence, we aimed construct describing between risk LET brainstem.Materials MethodsA matched case-control cohort (n=28, 1:3 ratio) symptomatic was selected from 954 paediatric ependymoma brain tumour patients treated passively scattered therapy. Dose-averaged (LETd) parameters restricted volumes (L50%, L10% L0.1cm3, cumulative LETd) within high-dose thresholds were included linear- logistic regression normal tissue complication probability (NTCP) models.ResultsA 1 keV/µm increase volume receiving dose over 54 Gy(RBE) lead an increased [confidence interval] 2.5 [0.0, 7.8] percentage points. The corresponding model had area under receiver operating characteristic curve (AUC) 0.76, increasing 0.84 anterior pons substructure as secondary parameter. 19 [7, 350] required associate (D > Gy(RBE)) 80% statistical power.ConclusionThe established illustrate impact high regions doses brainstem, thereby support mitigation clinical