⁃ I1. Age ≥ 12 years at the day of consenting to the study;

⁃ I2. Patients must have histologically confirmed diagnosis of primary bone sarcoma including but not limited to: Osteosarcomas, Ewing sarcomas, Chondrosarcomas, Undifferentiated Pleomorphic Sarcomas (UPS), Leiomyosarcomas (LMS) and Angiosarcomas;

⁃ I3. Prior treatment for localized or metastatic disease for bone sarcoma must have been completed, consisting of a standard multimodal treatment based on the histological subtype:

⁃ For OS, (excepted head and neck localisations), neoadjuvant and/or adjuvant chemotherapy should include methotrexate-based regimen for patients \< 18 years old; patients ≥ 18 years old may have received either methotrexate-based regimen or anthracycline and cisplatin-based regimen For head and neck OS, neoadjuvant and/or adjuvant chemotherapy should include adriamycin, cisplatin or ifosfamide-based regimen.

⁃ For non-OS, neoadjuvant and/or adjuvant chemotherapy should include adriamycin and/or cisplatin-based regimen.

⁃ I4. Recovery to NCI-CTCAE v5 Grade 0 or 1 level or recovery to baseline preceding the prior treatment from any previous drug/procedure related toxicity (except alopecia, anaemia, and hypothyroidism);

⁃ I5. Interval between the last chemotherapy administration and the date of randomisation: at least 4 weeks but no longer than 2 months;

⁃ I6. Confirmed complete remission or no evidence of disease (for metastatic disease);

⁃ Patients with pulmonary micro nodules can be included provided they do not meet the following criteria:

• At least one lung nodule of 10mm or more

• And/or at least two nodules well limited between 6-9mm

• And/or at least 5 nodules well limited of 5mm or less All the other situations will be considered as doubtful lesions except in case of metastatic disease confirmed during the lung surgery of the residual lung lesions after pre-operative chemotherapy. If no other metastatic localisation is detected at the initial staging, the patient will be considered as localised disease and eligible for randomisation.

⁃ I7. Life expectancy of greater than 12 months;

⁃ I8. Karnofsky Performance status ≥70 (patients younger than 18-year old) or ECOG performance status \< 2 (adult patients) ;

⁃ I9. Patients must have adequate bone marrow, renal, and hepatic function, as evidenced by the following within 7 days of study treatment initiation:

• Absolute neutrophil count ≥ 1.5 Giga/l

• Platelets ≥ 100 Giga/l

• Haemoglobin≥ 9 g/dl

• Serum creatinine ≤ 1.5 x ULN

• Glomerular filtration rate (GFR) ≥30 ml/min/1.73m2 according to the Modified Diet in Renal Disease (MDRD) abbreviated formula

• AST and ALT ≤2.5 x ULN ( ≤5.0 × ULN for patients with liver involvement of their cancer)

• Bilirubin ≤1.5 X ULN

• Alkaline phosphatase ≤2.5 x ULN (≤5 x ULN in patient with liver involvement of their cancer). If Alkaline phosphatase \> 2.5 ULN, hepatic isoenzymes 5-nucleotidase or GGT tests must be performed; hepatic isoenzymes 5-nucleotidase must be within the normal range and/or GGT \< 1.5 x ULN.

• Lipase ≤1.5 x ULN

• Spot urine must not show ≥ 1 +protein in urine or the patient will require a repeat urine analysis. If repeat urinalysis shows 1 + protein or more, a 24-hour urine collection will be required and must show total protein excretion \<1000 mg/24 hours

⁃ I10. INR/PTT ≤1.5 x ULN; Patients who are therapeutically treated with an agent such as warfarin or heparin will be allowed to participate provided that no prior evidence of underlying abnormality in coagulation parameters exists. Close monitoring of at least weekly evaluations will be performed until INR/PTT is stable based on a measurement that is pre-dose as defined by the local standard of care;

⁃ I11. Women of childbearing potential and male patients must agree to use adequate contraception (Appendix 4) for the duration of treatment and for 7 months (210 days) in WOCBP or 4 months (120 days) in men sexually active with WOCBP after the last dose of regorafenib;

⁃ I12. Women of childbearing potential must have a negative serum β-HCG pregnancy test within 7 days prior randomization and/or urine pregnancy test within 48 hours before the first administration of the study treatment;

⁃ I13. Patients, and their parents when applicable, must sign and date an informed consent document indicating that they have been informed of all the pertinent aspects of the trial prior to enrolment;

⁃ I14. Patients must be willing and able to comply with scheduled visits, treatment plan, laboratory tests and other study procedures;

⁃ I15. Patients covered by a medical insurance.

⁃ I16. Body Surface Area (BSA) ≥ 1.30m² at the time of consenting to the study.