Linear energy transfer-inclusive brainstem necrosis risk models applied to an independent paediatric proton therapy cohort

Radiation-induced brainstem necrosis is a severe toxicity that can occur following radiotherapy of tumours in the vicinity of the brainstem. Paediatric patients may be particularly at risk of brainstem necrosis since central nervous system (CNS) tumours are common paediatric diagnoses and the brainstem is central to children’s neurological and cognitive development. In a previous study, normal tissue complication probability (NTCP) models were fitted that describe symptomatic brainstem necrosis in paediatric ependymoma patients. In the study, a trend of increased dose-averaged LET (LET_d) in the high dose volume of the brainstem for the cases was identified. However, NTCP models are specific to the patients on which the models are fitted and an important part of NTCP modelling is to investigate how the models perform in an independent cohort.

The present study published in Acta Oncologica therefore aimed to apply the models in an independent paediatric patient cohort. First author Andreas Handeland is PhD student at UiB and Haukeland University Hospital and associate member of the Bioproton project..

The models estimated low risk of brainstem necrosis and the study showed that that the risk could be further reduced using LET optimisation. The importance of robustly optimising proton plans in terms of both dose and LET highlighted since LET may also have an impact on the NTCP of the patient.