ESTRO 2025 - Abstract Book

S1633

Clinical – äediatric tumours

ESTRO 2025

2636

Mini-Oral Proton beam therapy for intracranial germ cell tumors in pediatric, adolescent, and young adult patients: Kobe Proton Center experience Yumi Kokubo 1,2 , Yusuke Demizu 1 , Kazuma Iwashita 1 , SungChul Park 1 , Nobuyoshi Fukumitsu 1 , Tsuyoshi Suzuki 3 , Atsufumi Kawamura 4 , Daiichiro Hasegawa 5 , Yoshiyuki Kosaka 5 , Masaki Kokubo 2 , Toshinori Soejima 6 , Sunao Tokumaru 1 1 Department of Radiation Oncology, Kobe Proton Center, Kobe, Japan. 2 Department of Radiation Oncology, Kobe City Medical Center General Hospital, Kobe, Japan. 3 Department of Anesthesiology, Kobe Proton Center, Kobe, Japan. 4 Department of Neurosurgery, Kobe Children's Hospital, Kobe, Japan. 5 Department of Pediatric Oncology, Kobe Children's Hospital, Kobe, Japan. 6 Department of Radiation Oncology, Kobe Minimally Invasive Cancer Center, Kobe, Japan Purpose/Objective: The purpose of this study was to evaluate the outcomes of pediatric, adolescent and young adult (AYA) patients with intracranial germ cell tumor (ICGCT) treated with proton beam therapy (PBT) at Kobe Proton Center (KPC). Material/Methods: We retrospectively analyzed patients who received PBT for ICGCT at KPC between March 2018 and December 2023. The inclusion criteria were as follows: (1) patients who were diagnosed with ICGCT pathologically or clinically based on tumor markers and typical image findings, and (2) patients who were 20 of age or younger at the diagnosis. Patients who were followed up for less than 6 months were excluded. We calculated overall survival (OS) and progression-free survival (PFS) by the Kaplan-Meier method. Acute and late adverse events (AEs) were investigated based on Common Terminology Criteria for Adverse Events v. 5.0. Results: Twenty-nine patients were taken forward for the final analysis. The median age at the diagnosis was 12 (range, 5– 18) years. Seventeen patients were diagnosed with pure germinoma (PG), and 12 were diagnosed with non germinomatous germ cell tumor (NGGCT). The tumor locations were pineal gland (45%), suprasellar region (34%), basal ganglia (7%), bifocal (7%), and multifocal (7%). No patient had metastases. Two patients had a history of intracranial radiotherapy. Most patients received upfront systemic chemotherapy with cisplatin/carboplatin and etoposide, followed by PBT. The median prescribed dose-fractionation was 25.2 Gy (relative biological effectiveness [RBE]) in 14 fractions in the PG group, and 48.6 Gy (RBE) in 21 fractions in the NGGCT group. The treatment volume was described as whole ventricular/craniospinal/whole brain ± local irradiation. The median follow-up periods were 54 months. The 4-year OS/PFS rates in the PG and NGGCT groups were 100%/100% and 92%/90%, respectively (Fig. a, b). Two patients relapsed, and both of them were loco-regional recurrences. No grade 3 or higher acute AEs were observed. Until the latest follow-up, 7 patients (24%) suffered from grade 2 or higher late AEs, including 6 endocrine disorders, 2 hearing impairments, and 1 seizure (overlapped). All patients attended regular classes at school after PBT, except for one with a developmental disability. Nine patients graduated from high school and either pursued higher education or secured employment.