Ewing's sarcoma and related tumours (ESFT) are rare tumours, with a peak incidence in the second decade of life. They start most often from bone, and are characterized by a specific translocation involving the so-called EWS gene. In one patient out of three, the staging procedures detect metastatic tumours at the diagnosis, most commonly in lungs, bones, and bone marrow.

ESFT treatment strategy is multidisciplinary, combining primary chemotherapy, a local treatment, and consolidation chemotherapy.

The primary metastatic dissemination is the most important prognostic factor, as the survival rate is around 70-75% for localized tumours, in contrast with less than 50% for patients with primary metastatic disease.

Among primary metastatic patients, bone involvement and / or bone marrow strike markedly the prognosis of these patients. While the long-term survival of patients with isolated pleural pulmonary metastases is approximately 50%, whereas it is only from 0 to 25% in patients with bone marrow involvement.

In 1999, the Intergroup EURO EWING built a new study protocol for patients with Ewing tumours. For the patients with primary extrapulmonary metastatic Ewing tumours (R3 patients), the protocol proposed a heavy induction chemotherapy, in order to propose a consolidation with high dose chemotherapy to a higher rate of patients. The high-dose Busulfan Melphalan chemotherapy (BuMel) was based on Busulfan (600 mg/m²) and Melphalan (140 mg/m²), with autologous peripheral blood stem cell (PBSC) support.

Of note, for the full population of patients with metastatic disease, the 3-year EFS rate was 27% (SD 3%), and the OS rate was 34% (SD 4%), with a median follow-up of 3.9 years after diagnosis, and a median survival time of 1.6 years.

Ewing's sarcoma and related tumours (ESFT) are rare tumours, with a peak incidence in the second decade of life. They start most often from bone, and are characterized by a specific translocation involving the so-called EWS gene. The gene rearrangement results in the production of a transcription factor, in the majority EWS-FLI1 transcription.

In one patient out of three, the staging procedures detect metastatic tumours at the diagnosis; metastases involve most commonly lungs, bones, and bone marrow.

Therefore, in addition to local imaging, the initial extension assessment of any Ewing tumour includes at least a chest CT scan, and a bone marrow extensive evaluation, comprising bone marrow punctures into several different sectors, bone marrow biopsies, and a bone imaging evaluation. The FDG-PET scan is more sensible than bone scan and conventional imaging as MRI in detection of bone metastases. It is more and more widely used in the bone metastasis search in Ewing tumours and seems useful to complement the search of extra-osseous metastases (outside the lungs), including that of bone marrow metastases. The full-body MRI is still under evaluation for the disease extension evaluation.

ESFT treatment strategy is multidisciplinary, combining primary chemotherapy, a local treatment, and consolidation chemotherapy. The local treatment may combine surgery and / or radiotherapy, according to the tumour site and size, and to the tumour response. ESFT chemotherapy is based on alkylating agents (ifosfamide and / or cyclophosphamide), etoposide, anthracyclines, vincristine, and actinomycin.

The primary metastatic dissemination is the most important prognostic factor, as the survival rate is around 70-75% for localized tumours, in contrast with less than 50% for patients with primary metastatic disease. Among primary metastatic patients, bone involvement and / or bone marrow strike markedly the prognosis of these patients. While the long-term survival of patients with isolated pleural pulmonary metastases is approximately 50%, whereas it is only from 0 to 25% in patients with bone marrow involvement.

In 1999, the Intergroup EURO EWING built a new study protocol for patients with Ewing tumours, localized or metastatic and below 50 years of age. For the patients with primary extrapulmonary metastatic Ewing tumours (R3 patients), the protocol proposed a heavy induction chemotherapy, in order to propose a consolidation with high dose chemotherapy to a higher rate of patients. The high-dose BuMel chemotherapy was based on Busulfan (600 mg/m²) and Melphalan (140 mg/m²), with autologous peripheral blood stem cell (PBSC) support.

The study enrolled 281 patients with primary dissemination and skeletal metastases, with or without bone marrow involvement and with or without additional pulmonary metastases or metastases to other sites. In contrast to the distribution in the entire group of patients with Ewing tumours, the primary site in this subgroup was extremity in only 31% patients, pelvis/abdomen in 45%, and axial/other in 24% patients. The overall survival at 3 years was 28% (SD 4%) in the group with primary tumour in the abdomen or pelvis, versus 39% (SD 6%) for each of the two other groups. Of note, for the full population of patients with metastatic disease, the 3-year EFS rate was 27% (SD 3%), and the OS rate was 34% (SD 4%), with a median follow-up of 3.9 years after diagnosis, and a median survival time of 1.6 years.

Inclusion Criteria:

1. - Ewing tumour histologically or cytologically confirmed, harboring a specific transcript, and with extrapulmonary metastases (including nodal extension) - histology and FISH results must be consistent, specific transcript can be obtained after inclusions.

2. - Ewing tumour not previously treated.

3. - Age between 2 and 50 years.

4. - Measurable disease by cross sectional imaging (RECIST 1.1) or evaluable disease with functional metabolic, positron emission tomography scanner (PET SCAN) or other methods (e.g., cytology/histology).

5. - General status compatible with the study treatments (LANSKY score ≥ 50%, or Karnofsky ≥ 50%, or Eastern Cooperative Oncology Group (ECOG) ≤ 2).

6. - Adequate bone marrow function (not applicable in case of bone marrow disease).

   • Platelets ≥ 100 x 109 /L
   • Absolute Neutrophil Count (ANC) ≥ 1 x 109 /L
   • Hemoglobin ≥ 8g /dL.

7. - Adequate liver function :

   • Aspartate Aminotransferase (AST) and Alanine Transferase (ALT) ≤ 5 x Upper Limit Normal (ULN)
   • Total Bilirubin ≤ 2 Upper Limit Normal (ULN). If total bilirubin > 2xULN, Bilirubin Conjugated Fraction (BCF) ≤ 2 x ULN

8. - No absolute contra-indication of Busulfan-Melphalan if radiotherapy of the primary tumour is necessary with specific attention to patient with primary spinal tumor.

9. - Adequate cardiac and renal functions:

   • Creatinine < 1.5 of normal for age or clearance > 60 ml/min/1.73 m²;
   • Left Ventricular Ejection Fraction (LVEF) > 50% and/or shortening fraction > 28%.

10. - No underlying disease contra-indicating the study treatments.

11. - Patient likely compliant with the recommended study medical monitoring during and after treatments.

12. - Patients of childbearing potential must agree to use adequate contraception for the duration of study treatments and up to 12 months for women and 6 months for men following completion of therapy.

13. - Females of childbearing potential must have a negative serum β-human chorionic gonadotropin (HCG) pregnancy test within 10 days prior study inclusion, and/or urine pregnancy test within 48 hours before the first administration of the study treatment.

14. - Patients covered by a health insurance system.

15. - Patient, or patient's legal representative, informed and having signed the informed consent.

Exclusion Criteria:

1. - Age below 2 or greater than 50 years.
2. - Ewing tumour localized, or solely with pleural and/or lung metastases.
3. - Concomitant disease, particularly infectious disease, likely to interfere with patient's treatment.
4. - History of cancer, according to investigator's judgment.
5. - Life expectancy < 2 months.
6. - Patient already included in another clinical trial with an investigational drug.
7. - Pregnant or breastfeeding patient.
8. - Person deprived of liberty or under guardianship.
9. - Patient likely unable to comply with the study medical monitoring for geographical, social or psychological reasons.

Sponsor will share de-identified data sets. Documents generated under the project will be disseminated in accordance with Institut Curie policies.

Data requests can be submitted starting 9 months after last article publication and will be made accessible for up to 12 months.

Access to trial individual participant data can be requested by qualified researchers engaging in independent scientific research, and will be provided following review and approval of a research proposal and Statistical Analysis Plan (SAP) and execution of a data sharing agreement (DSA).