Oral Liquid 13-cis-retinoic Acid (13-CRA)

Inclusion Criteria: 1. Male or female aged from 0 years to \< 21 years of age. 2. Patient with high risk neuroblastoma, or unresectable, unfavourable histology intermediate risk neuroblastoma the latter age ≥ 18 months at diagnosis 3. Patient who is scheduled to receive at least two treatment cycles of 13-CRA. 4. Patient who cannot swallow 13-CRA capsules (i.e. requires extraction of 13-CRA from the capsules). 5. Negative pregnancy test for females of child-bearing potential before initiation of treatment, and sexually active patients and partners agreeing to undertake adequate contraceptive measures (see section 4.5). 6. Provision of a single or double lumen central venous catheter for sampling (i.e. already in place). 7. Parent(s)/legal guardian able and willing to provide written informed consent for the patient to take part in the trial. 8. Where applicable, the patient should assent to undergo blood sampling for pharmacokinetic purposes and to allow physiological measurements to be made. Exclusion Criteria: 1. Any clinically significant medical condition or abnormality, which, in the opinion of the investigator, might compromise the safety of the patient or which might interfere with the trial. 2. Diagnosis of high-risk neuroblastoma (HRNBL) which is currently being treated on the SIOPEN HRNBL trial (patients who have exited this trial will be eligible). 3. Known allergy to 13-CRA or any of the excipients. 4. Inadequate contraception measures in females of childbearing age. 5. Receiving concomitant treatment with tetracyclines. Prior to each cycle: 1. Total bilirubin ≤ 1.5 x normal, and (SGPT) ALT ≤ 5 x normal. Veno-occlusive disease if present, should be stable or improving. 2. Skin toxicity no greater than CTCAE Grade 1(10) 3. Serum triglycerides \<5.65mmol/L. 4. No haematuria and / or proteinuria on urinalysis. 5. Serum calcium ≤ 2.9mmol/L. 6. Serum creatinine based on age / gender as follows: Age Maximum Serum Creatinine µmol/L Male Female 1 month to \< 6 months 35 35 6 months to \< 1 year 44 44 1 to \< 2 years 53 53 2 to \< 6 years 70 70 6 to \< 10 years 88 88 10 to \< 13 years 106 106 13 to \< 16 years 132 124 ≥ 16 years 150 124 7. Patients with a seizure disorder must be well controlled and taking anticonvulsants. CNS toxicity \< grade 2 (CTCAE). Withdrawal Criteria: 1. Positive pregnancy test - pregnancy testing will be undertaken before treatment commences and routinely before each course of treatment in females of childbearing potential. If a patient is found to be pregnant during the trial, the next course of treatment will not be given until the pregnancy has been discussed with the treating clinician, and the patient will be withdrawn from the trial whether or not treatment is continued. 2. Request of the patient, for any reason. 3. Discretion of the investigator.