The single-arm phase 1 study NO18517 (NCT00532948) assessed the maximum tolerated dose and dose-limiting toxicities of capecitabine (Xeloda®) administered concurrently with radiation therapy in children with newly diagnosed diffuse intrinsic brain stem gliomas and high grade gliomas. Patients in the phase 1 study NO18517 who were diagnosed with intrinsic brainstem glioma and who were treated at the established maximum tolerated dose of capecitabine 650 mg/m^2/dose twice a day were included in the analyses of the phase 2 study NO21125.