C. Matuschek1, D. Sohn2, W. Budach1, J. Haussmann1, E. Boelke1, B. F. Tamaskovics3, and D. Jazmati4; 1Department of Radiation Oncoloy, Heinrich Heine University, Dusseldorf, Germany, 2Heinrich Heine University, Dusseldorf, Germany, 3Heinrich Heine University, Düsseldorf, Germany, 4Medical Faculty Heinrich Heine University, Dusseldorf, Germany
Purpose/Objective(s): Medulloblastoma is the most common malignantpediatric brain tumor, necessitating normofractionated craniospinal irradiation (CSI) with an additional boost over about 6 weeks in children older than 3 years. This study investigates the sensitivity of pediatric medulloblastoma cell lines to different radiation fractionation schedules. While extensively studied in adult tumors, these ratios remain unknown in pediatric cases due to the rarity of the disease. Materials/Methods: Five distinct medulloblastoma cell lines (ONS76, UW228-3, DAOY, D283, D425) were exposed to varying radiation doses and fractionation schemes. In addition, ONS76 and UW2283-3 stably overexpressing c-Myc were analyzed. Alpha/beta values, representing fractionation sensitivity, were quantified using the linear-quadratic model of radiation survival. Results: The study unveiled elevated alpha/beta ratios across diverse medulloblastoma cell lines, with a mean alpha/beta value of 25.01 (ranging from 8.42 Gy to 75.09 Gy). Neither TP53 status nor the levels of MYC expression influenced fractionated radiosensitivity. Furthermore, no significant differences in alpha/beta values were observed among various medulloblastoma subgroups. Conclusion: These in vitro findings strongly recommend normofractionated or hyperfractionated radiotherapy for pediatric medulloblastoma cases due to consistently high Alpha/Beta values across subgroups. Conversely, hypofractionated radiotherapy is not advisable. This study highlights the potential for personalized dosage prescriptions, improving patient prognosis and safety.
