Metronomic Chemotherapy in Wilms Tumor (MetroWilms-1906)

Inclusion Criteria:

* Patient ≥18 months old and ≤ 17 years old
* Relapsed or refractory Wilms tumor, histologically proven at diagnosis
* After at least 2 lines of chemotherapy (conventional or high dose, which may include the trial molecules) or after 1 line for high risk relapse for which there would not be any curative therapy. If 1 line for high risk relapse, the enrolment should be confirmed by coordinators.
* Radiologically measurable or evaluable disease (visible, target or non-target-lesion on MRI or CT-scan)
* Performance status: Karnofsky performance status (for patients \>16 years of age) or Lansky Play score (for patients ≤16 years of age) ≥ 70%.
* Able to take oral medication or nasal gastric tube or authorized gastrostomy
* Adequate biological criteria:

  * Neutrophils \> 1000/mm3 ; Platelets \> 75 000/mm3
  * Transaminases (ALT/ AST) ≤ 3 times ULN (or ≤ 6 times ULN if liver metastasis); total bilirubin ≤ 2 ULN (except in case of Gilbert's disease)
* Creatinine ≤ 1,5 ULN or clearance ≥ 60 mL/ min/ 1,73m2 (In case of doubt, to be confirm by assessment of cystatin )
* Females of childbearing potential must have a negative seric pregnancy test within 7 days prior to initiation of treatment.
* Sexually active patients must agree to use adequate and appropriate contraception (at least one highly effective contraception or two complementary methods of contraception), 1 month before beginning of treatment while on trial drug and for 7 months after stopping the trial drug for female patients and after 6 months for male patients.
* Written informed consent from parents/legal representative, patient, and age-appropriate assent before any trial-specific screening procedures according to national guidelines.
* Patient covered by the French "Social Security" regime

Exclusion Criteria:

* Prior history of other cancer within 5 years
* Chemotherapy or radiotherapy of target lesion within 3 weeks prior to inclusion
* Target therapy within less than 5 \* half-life of the substance prior to inclusion
* Major surgery within 15 days prior to inclusion
* Presence of any NCI-CTCAE v5 grade ≥ 2 cardiac, hepatic, pulmonary or renal toxicity
* Severe myelosuppression
* Severe peripheral neuropathy (grade ≥ 2)
* Fructose intolerance
* Inflammatory bowel chronic disease and/or intestinal obstruction
* Patients with demyelinating form of Charcot-Marie-Tooth disease
* Known active viral hepatitis or known human immunodeficiency virus (HIV) infection or any other uncontrolled infection.
* Known hypersensitivity to dacarbazine (DTIC), isotretinoin or to any of the trial drugs, trial drug classes, excipients in the formulation
* Hyperlipidemia and hypervitaminosis A
* Vaccination with a live attenuated vaccine within 1 month prior to inclusion
* Pregnant or breastfeeding patients
* Inability to comply with medical follow-up of the trial (geographical, social or psychological reasons)