Representing about 10% of brain tumours, they are most often located in the middle part of the posterior fossa within the fourth ventricle, but with possible extensions within it, and down to the cervical spinal canal, which complicates the radiotherapy technique. They may be encountered in very young child (especially in the hemispheres).

Their aggressiveness is partly determined by the histological aspect, the diffuse anaplastic forms being the most malignant. These forms and less aggressive but incompletely operated ones must be irradiated.
Studies to demonstrate the impact of increased radiation doses on tumour control are under way.

The position of proton therapy

Several reasons may militate in its favour when some or all of them are brought together (young age, technical complexity, and need for dose escalation).

Schedule of irradiation

Daily sessions, spread over approximately 6 to 7 weeks.