Brief Summary: This phase I trial is studying the side effects and best dose of cilengitide in treating children with recurrent, progressive, or refractory primary CNS tumors. Cilengitide may slow the growth of brain cancer cells by stopping blood flow to the tumor.

Detailed Description: PRIMARY OBJECTIVES: I. To describe the acute and dose-limiting toxicities (DLT) and define the maximum tolerated dose (MTD) of cilengitide (EMD 121974) when administered to children and adolescents with refractory primary brain tumors. SECONDARY OBJECTIVES: I. To obtain preliminary evidence of biologic activity by determining alterations in tissue perfusion, tumor blood flow and metabolic activity using MR perfusion, PET and MRS and correlating these findings with changes in tumor size by volumetric MRI. II. To characterize inter- and intra-patient variability in the pharmacokinetics of cilengitide and to estimate cilengitide renal clearance in this patient population. III. To characterize the pharmacogenetic polymorphisms in drug transporters (e.g., MRP4, BCRP) and relate to cilengitide disposition. IV. To evaluate changes in circulating endothelial cells (CECs) and circulating endothelial precursors (CEPs) in patients treated with cilengitide, and to investigate the correlation between changes in CECs and CEPs, plasma, serum and urine angiogenic protein levels such as VEGF, and clinical outcome. V. To obtain preliminary information about the efficacy of cilengitide in this patient population. OUTLINE: This is a dose-escalation, multicenter study. Patients receive cilengitide (EMD 121974) IV over 1 hour twice weekly. Treatment repeats every 4 weeks for 13 courses in the absence of disease progression or unacceptable toxicity. Cohorts of 3-6 patients receive escalating doses of cilengitide until the maximum tolerated dose (MTD) is determined. The MTD is defined as the dose at which 25% of patients are expected to experience dose-limiting toxicity. Once the MTD is determined, 6 additional patients are accrued and treated at that dose level for a total of 12 patients at the MTD. Patients receiving treatment are followed weekly for the first three months then monthly for one year or 13 courses of treatment. Patients discontinuing treatment will be followed for resolution of all adverse events occurring while on treatment and/or within 30 days of the last administration of study drug. Patients will be followed for the shortest of 1) three months after the last protocol based treatment, or 2) the date other therapy is initiated.