Inclusion Criteria:
To be eligible to participate in this trial, an individual must meet all the following criteria:
1. ≤ 18 years.
2. Participants must have a diagnosis of:
1. De novo or recurrent abdominal soft-tissue sarcoma.
2. De novo or recurrent high-risk neuroblastoma according to Children's Oncology Group (COG) risk classification, regardless of response to frontline therapy, diagnosed either by a former histologic verification of neuroblastoma and/or former demonstration of tumor cells in the bone marrow with increased urinary catecholamines at the time of study enrolment. Participants who were initially considered low or intermediate risk but were then reclassified as high risk are also eligible.
3. Other tumors: recurrent Wilms tumor, de novo or recurrent Germ cell tumour, de novo or recurrent extracranial malignant rhabdoid tumor, de novo or recurrent synovial sarcoma, de novo or recurrent fibrolamellar hepatocellular carcinoma, and de novo or recurrent desmoplastic small round cell tumor.
3. A histology assessment is required for enrolment of de novo cases, except for patients with high-risk neuroblastoma for which a radioiodine-labelled meta-iodobenzyl-guanidine (MIBG) test is positive and excess of production od catecholamines is confirmed. A new histology assessment is not required for enrolment of the recurrent cases, it will be obtained from the resected tumor to assess whether the histology is identical to the original tumor.
4. Participants previously treated with irinotecan will be eligible if they have not had documented progressive disease during treatment.
5. Participants might have more than one surgically removable lesion.
6. Adequate liver, renal, hematological, and cardiac function as defined by biochemical and hematological parameters as follows: hemoglobin (Hb) \>9.0 g/dL (with preoperative transfusion), platelets \>80.000/mm3 with intraoperative transfusion, absolute neutrophil count ≥ 1.500/mm3 or below this threshold if there is clinical indication that the patient is on hematological recovery, albumin \>3.0 g/dl, alanine aminotransferase (ALT) and aspartate aminotransferase (AST) \<2.5 times the upper limit of normality \[ULN\], bilirubin \<2 times the ULN, creatinine \<1.0 mg/dl or creatinine clearance \> 60 ml/min.
7. Participants must have fully recovered from the acute toxic clinically relevant effects (Grade 3 or above) of all prior chemotherapy, immunotherapy, or radiotherapy prior to entering this trial.
8. Lansky or Karnofsky functional performance status score ≥ 50 at screening.
9. Female participants of childbearing potential must have a negative urine beta-human chorionic gonadotropin (beta-hCG) pregnancy test at time of screening.
10. Female and male participants of childbearing potential must be willing to use adequate contraception throughout the study and for 6 months after surgery.
11. Life expectancy greater than 6 months.
12. The participant's legally authorized guardian must acknowledge in writing that consent to become a study subject has been obtained prior to any protocol screening procedures.
Exclusion Criteria
An individual who meets any of the following criteria will be excluded from participation in this trial:
1. Metastatic lesions, that in the investigator's opinion will not jeopardize the assessment of efficacy and safety.
2. Other malignancies within past 2 years except for in-situ cancers or basal/squamous cell skin cancer. Subjects with other malignancies are eligible if they are disease-free for at least 24 months or have a clinically stable concurrent malignancy not requiring tumor-directed treatment.
3. Active bacterial, viral or fungal infection.
4. Known history of active human immunodeficiency virus (HIV) infection, hepatitis B, hepatitis C or chronic liver disease. Testing is not required in the absence of clinical findings or suspicion.
5. Impossibility of ensuring adequate follow-up.
6. Participants who, in the opinion of the investigator, may not be able to comply with the safety monitoring requirements of the study.
7. Contraindication to computed tomography (CT) scan.
8. Major surgery within 14 days prior to the implant of study drug or still in recovery after experiencing surgical complications; neither tumor biopsy nor central line insertion are considered a major surgery.
9. Other relevant concomitant illnesses.
10. Participants´status post-allogeneic stem cell transplant are not eligible.
11. Participants with disease of any major organ system that would compromise their ability to withstand therapy.
12. Patients with tumor size requiring CEB-01 implant that exceeds the maximum implantable surface area based on Body Surface Area (BSA) correction.
13. Patients with known hypersensitivity to SN-38 or any of the CEB-01 excipients.
14. Pregnancy or lactation. Pregnant women are excluded from this study; if the patient is a lactating mother, breastfeeding should be discontinued.
