Re-Irradiation of Progressive or Recurrent DIPG

Inclusion Criteria: All of these criteria must be met for a patient to be eligible for this study: 1. Each site may accept a patient on study of any age that they have permission to treat and follow on study per their institutional policy. 2. The patient has no evidence of metastases on cranial or spinal MR imaging 3. The patient has received RT in the past, given to a total cumulative dose of \<60 Gy; prior radiation using opposed lateral fields, conformal 3-D fields, IMRT or using protons is acceptable 4. At least 180 days have elapsed from the last day of primary RT for DIPG 5. The patient has recovered from all acute and subacute toxicities of prior RT and of chemotherapy, if chemotherapy was utilized in the past 6. The patient has been off all anti-tumour therapy for at least 14 days 7. The patient has a Lansky score of 40% or higher 8. The patient has a life expectancy anticipated to be at least 8 weeks with treatment using re-irradiation, with or without dexamethasone 9. The patient has no uncontrolled medical condition (e.g., seizures, diabetes, infection) that would interfere with the delivery of rRT 10. The patient agrees to not enroll on any other clinical trial of an anti-tumour intervention 11. The patient agrees to report and have recorded the use of all medications taken during ReRAD therapy, from the time of diagnosis of progression or recurrence, then through and after completion of, ReRAD therapy; this includes the use of complementary, alternative and dietary therapies 12. The patient is treated at a site where the study is approved by the local ethics board 13. Males and females of child-bearing potential must agree to use effective birth control measures during rRT 14. Consent, and, if applicable, assent, has been obtained according to institutional standards Exclusion Criteria: If the patient fulfills any of these criteria, then he or she will not be eligible for the study: 1. Females who are pregnant, due to risks from rRT on the developing fetus. 2. Any patient with a condition that prohibits the planned delivery of rRT as prescribed in this study. 3. Patients who are receiving any other clinical trial of an anti-tumour intervention