Long-Term Outcomes of Radiation Therapy for Pediatric Brain Tumors: A Single-Center Study

Brain tumors are the leading cause of mortality among pediatric patients. Recent advancements in genetic analysis have facilitated the development of new therapeutic agents, and high-precision radiotherapy techniques have improved survival rates for certain pediatric brain tumors. However, owing to the rarity of these tumors and the diversity of histological types, most treatment results are reported in clinical trials, and real-world data on the long-term treatment effects of radiotherapy in Japan are scarce. This study investigated the long-term outcomes of pediatric brain tumor treatment at a single institution. A total of 54 pediatric brain tumor patients aged ≤14 years who had undergone radiotherapy between 2007 and 2021 were included. Irradiation was performed using three-dimensional conformal or intensity-modulated radiation therapy. The distribution of each tumor type was as follows: eight diffuse intrinsic pontine gliomas, six malignant gliomas, 12 medulloblastomas, eight ependymomas, 15 germ cell tumors, and five other tumors (malignant peripheral nerve sheath tumor, pinealoblastoma, atypical teratoma/rhabdoid tumor, primitive neuroectoderm tumor, and malignant astroblastoma). The median follow-up duration for all patients and survivors was 48.4 months and 110 months, respectively. The one-, five-, and 10-year overall survival rates according to tumor type were as follows: diffuse intrinsic pontine glioma - 12.5%, 0%, and 0%; malignant glioma - 50%, 0%, and 0%; medulloblastoma - 91.7%, 83.3%, and 58.3%; ependymoma - 100%, 50%, and 37.5%; germ cell tumors - 93.3%, 93.3%, and 93.3%; and others - 80%, 80%, and 40%, respectively. The one-, five-, and 10-year progression-free survival rates according to the tumor type were 0% for both diffuse intrinsic pontine gliomas and malignant gliomas; 75%, 50%, and 50% for medulloblastoma; 62.5%, 25%, and not available for ependymoma; 86.7%, 80%, and 80% for germ cell tumor; and 60%, 40%, and not available for other tumors, respectively. Adverse events of grade 3 or higher (based on common terminology criteria for adverse events version 5.0) were observed in three patients as follows: two with hearing impairment and one with secondary cancer. Our findings revealed that the prognosis and recurrence patterns such as local and disseminated recurrence substantially differ depending on the tumor type. This confirms that each tumor type requires a unique approach. In recent years, significant progress has been made in the stratification and optimization of treatment through genetic analysis. However, to achieve improved tumor control and minimize late effects, the accumulation of long-term clinical data is essential.