Critères d'inclusion : - Pediatric patients in need of temozolomide (all indications with 5-day treatment per 21- or 28-day cycle).
- Male and female patients aged 1 to less than 18 years
- Patients who have signed the informed consent or for which one, both parents or legal guardian (depending on local legislation) have signed the informed consent.
- Patients having records of coverage by a health insurance
- Life expectancy ≥ 3 months
- Adequate haematological function:
*haemoglobin ≥ 80 g/L (transfusion support authorized)
*neutrophil count ≥ 1.0 x 10e9 cells/L
*platelet count ≥ 100 x 10e9 cells/L (without transfusion support)
*in case of bone marrow involvement: neutrophils ≥ 0.5 x 10e9 cells/L and platelets ≥75 x 10e9 cells/L
- Adequate renal function:
*Creatine clearance ≥ 60 mL/min.1.73m² according to the Schwartz formula  or its modified form 
- Adequate hepatic function:
*bilirubin ≤1.5 x ULN
*AST and ALT ≤ 2.5 x ULN (AST, ALT 5xULN in case of liver metastases)
- Lansky Score ≥ 70%
Critères de non-inclusion : - Patients who are co-administrated at day one with sodium valproate as it decreases the clearance of temozolomide
- Patients with (naso)gastric tube administration of temozolomide during first cycle of treatment.
- Patients already enrolled in studies investigating temozolomide or other investigational new drugs.
- A post-menarche female with a positive blood/urine pregnancy test at inclusion.
- Known contraindication or hypersensitivity to temozolomide or any chemically close substance