Outcome after Modern Proton Beam Therapy in Childhood Craniopharyngioma; Results of the Prospective Registry Study KiProReg.

BACKGROUND: Craniopharyngiomas (CPs) are rare tumours of the sellar region often leading to significant comorbidities due to their close proximity to critical structures. Aim of this study was to analyse survival outcome and late toxicities after surgery and proton beam therapy (PBT) in childhood CPs.

PATIENTS AND METHODS: Within the prospective XXXX study (XXXX), data of 74 childhood patients with CP, receiving PBT between 08/2013-06/2022 were eligible. Late toxicities were analysed according to the grading system of CTCAE 4.0.

RESULTS: Median follow-up (FU) since first diagnosis was 4.3 years (range, 0.8-14.7). 75.7% of patients received PBT at time of disease progression or recurrence, whereas 24.3% as part of their primary therapy (definitive or adjuvant). Predominantly (85.1%), pencil beam scanning technique was used. Median total dose and initial tumour volume were 5400 cGyRBE (relative biological effectiveness) and 17.64 cm³ (range, 3.07-300.59), respectively. The estimated (±SE) 3-year overall survival, progression-free and cystic failure-free survival rate after PBT were 98.2% (±1.7), 94.7% (±3.0), and 76.8% (±5.4), respectively. All local failures (n=3) were in-field relapses necessitating intervention and occurred exclusively in patients receiving PBT at progression or recurrence. Early cystic enlargements after PBT were typically asymptomatic and self-limiting. Fatigue, headaches, vision disorders, obesity and endocrinopathies were the predominant late toxicities. No high grade (≥3) new-onset visual impairment or cognitive deterioration occurred compared to baseline. The presence of cognitive impairments at the end of FU correlated with size of the planning target volume (p=0.034), Dmean dose to the temporal lobes (p=0.032,p=0.045) and the number of surgical interventions prior to PBT (p=0.029).

CONCLUSIONS: Our findings demonstrate favourable local control rates using modern PBT with acceptable late toxicities. Cyst growth within 12 month after radiotherapy is typically not associated with tumour progression. Longer FU has to be awaited to confirm results.