RE-irradiation of Diffuse MIdline Glioma paTients

To evaluate the safety of re-irradiation (reRT)

The primary endpoint will be the cumulative incidence of grade ≥4 CTCAE (The NCI Common Terminology Criteria for Adverse Events) events measured 4 weeks after the last day of reRT.

The key secondary objective is to prospectively validate the palliative efficacy of reRT of DMG. Palliative efficacy is evaluated by two endpoints: overall survival and symptom relief.

Palliative efficacy measured as overall survival will be reported as 1) from date of diagnosis to date of death by any cause, and 2) from date of first radiological and/or clinical progression to date of death by any cause.

Palliative efficacy measured as symptom relief

Symptom relief measured by 1) clinical performance status (Karnofsky or Lansky) assessed every second week, 2) a modified PEDI score before, during and 4 weeks after reRT, 3) steroid dose levels measured every second week, and 4) quality of life monitored before, during and 4 weeks after re-irradiation with PedsQL Cancer module questionnaire.

Other secondary outcomes

Other secondary objectives are further defined as: * Image-guided characterization of the anatomical site of progression compared to the primary lesion. * Assessment of cumulated radiation dose to critical structures in the brain following the initial and reRT treatment.

Exploratory analyses

* Delineation study A comparison of variations in delineation in tumour volume among the participating institutions. This will improve the delineation-related uncertainty and, consequently, the applied margins (and hence irradiated volume) can be diminished. This will ensure a more uniform treatment across countries. * The impact of reRT on the patients and their families An analysis of the value of reRT in terms of the practical, emotional, and existential impact on patients and their families. This will be done by using a qualitative method including interviewing the parents of a subgroup of the included patients. * Referral patterns A characterisation of referral patterns of DMG patients to reRT. This will be assessed through a screenings log of all DMG patients in the participating institutions. Date of diagnosis, date of death, reRT offered yes/no, and reason for not giving reRT will be registered prospectively.