Capecitabine and Radiation Therapy in Treating Young Patients With Newly Diagnosed, Nonmetastatic Brain Stem Glioma or High-Grade Glioma

OBJECTIVES: Primary * Estimate the maximum tolerated dose of capecitabine rapidly disintegrating tablets (RDT) administered concurrently with radiotherapy in young patients with newly diagnosed, nondisseminated intrinsic brain stem glioma or high-grade glioma. * Describe the dose-limiting toxicity in patients treated with this regimen. Secondary * Describe the safety profile of this regimen. * Characterize the pharmacokinetics of capecitabine RDT in these patients. * Explore the exposure-response relationship for measures of safety and effectiveness using pharmacokinetic and pharmacodynamic models. * Describe the antitumor activity of this regimen observed in these patients. * Estimate distributions of progression-free survival and survival in patients treated with this regimen. * Characterize radiographic changes in tumor, using MRI, perfusion and diffusion MRI, and positron emission tomography (PET) scans, in patients treated with this regimen. OUTLINE: This a multicenter, dose-escalation study of capecitabine rapidly disintegrating tablets (RDT). Patients undergo radiotherapy once daily, 5 days a week, for approximately 6 weeks. Beginning within 24 hours of starting radiotherapy, patients also receive oral capecitabine RDT twice daily on days 1-21. Treatment with capecitabine RDT repeats every 21 days for 3 courses. Cohorts of 3-6 patients receive escalating doses of capecitabine RDT until the maximum tolerated dose (MTD) is determined. The MTD is defined as the dose preceding that at which 2 of 3 or 2 of 6 patients experience dose-limiting toxicity. Beginning in week 12, patients receive capecitabine RDT at a fixed dose twice daily on days 1-14. Treatment repeats every 21 days for 3 courses in the absence of disease progression or unacceptable toxicity. Patients undergo blood collection periodically during course 1 for pharmacokinetic correlative studies. Patients also undergo MRI, and rapid perfusion/diffusion MRI at baseline and periodically during study for radiographic correlative studies. After completion of study treatment, patients are followed periodically for 2 years. PROJECTED ACCRUAL: A total of 18 patients will be accrued for this study.