External Beam Radiation Therapy and Cetuximab Followed by Irinotecan and Cetuximab for Children and Young Adults With Newly Diagnosed Diffuse Pontine Tumors and High-Grade Astrocytomas

Inclusion Criteria:

* Patients must have either (1) histologic proof of a high-grade astrocytoma reviewed by a POETIC institutional pathologist or (2) a radiological diagnosis via MRI scan of a typical diffuse pontine tumor made by a POETIC institutional neuroradiologist. Patients with a radiological diagnosis via MRI scan of a typical diffuse pontine tumor will be enrolled on the diffuse pontine tumor arm of the study regardless of histology in cases that are biopsied. Note: For collaborating non-POETIC institutions, the reviews may be done by an institutional pathologist/neuroradiologist.
* Patients must begin study prescribed therapy within 42 days of neurosurgical resection or biopsy of the tumor (high-grade astrocytoma patients) or radiological diagnosis (diffuse pontine tumor patients).
* Age ≥ 3-years and \< 22-years-old.
* Brain MRI (and any other studies done according to clinical indications) must not show any definitive evidence of leptomeningeal or extra-neural metastases.
* ANC ≥ 1000/μL and platelet count ≥ 100,000/μL
* Patients must have adequate organ function as defined by:
* Hepatic: total bilirubin \< 1.5 mg/dl, AST ≤ 2.5 x the upper limit of normal.
* Renal: serum creatinine ≤ 1.5 x the upper limit of normal for age, or calculated creatinine clearance or nuclear GFR ≥ 70 ml/min/1.73 m2.
* The patient, or for minors, a parent or legal guardian, must give informed written consent indicating they are aware of the investigational nature of this study.

Exclusion Criteria:

* Evidence of leptomeningeal or extra-neural metastatic disease.
* Prior radiation therapy or chemotherapy
* Pregnancy, mothers unwilling to refrain from breast-feeding, and sexually mature patients unwilling to practice an effective form of birth control.
* Other significant concomitant medical illnesses that would compromise the patient's ability to receive all prescribed study therapy.
* Prior therapy which specifically and directly targets the EGFR pathway.
* Prior severe infusion reaction to a monoclonal antibody.
* Significant history of uncontrolled cardiac disease; i.e., uncontrolled hypertension, unstable angina, recent myocardial infarction (within prior 6 months), uncontrolled congestive heart failure, and cardiomyopathy with decreased ejection fraction.
* Patients with known Gilbert's Syndrome.