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

• I2. Patients must have histologically confirmed high-grade sarcomas of bone primary localisation, including but not limited to: Osteosarcomas, Ewing sarcomas, Chondrosarcomas, Undifferenciated Pleomorphic Sarcomas (UPS), Leiomyosarcomas (LMS) and Angiosarcomas

• I3. Evaluable residual disease not amenable to resection after multimodal treatment principles either at diagnosis (after standard multimodal treatment based on the histological subtype) or at relapse (chemotherapy)

• I4. Non progressive disease (defined by the investigator according to the RECIST version 1.1 Appendix 1) at study entry;

• I5. Interval between the date of last anticancer treatment (chemotherapy or surgery) and the start date of regorafenib: at least 4 weeks but no longer than 2 months;

• I6. Life expectancy of greater than 6 months;

• I7. Eastern Cooperative Oncology Group (ECOG) performance status \< 2 (Karnofsky ≥ 70%) (Appendix 2);

• I8. Adequate bone marrow and organ function defined by the following laboratory results:

• a. Bone marrow: i. Absolute neutrophil count ≥ 1.5 Giga/l ii. Platelets ≥ 100 Giga/l iii. Haemoglobin≥ 9 g/dl

• b. Hepatic function: i. Aspartate aminotransferase (AST) and Alanine aminotransferase (ALT) ≤ 2.5 x Upper Limit of Normal (ULN) (≤ 5.0 × ULN for patients with liver involvement of their cancer) ii. Bilirubin ≤1.5 X ULN iii. 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 gamma-glutamyltransferase (GGT) tests must be performed; hepatic isoenzymes 5-nucleotidase must be within the normal range and/or GGT \< 1.5 x ULN.

• c. Renal function: i. Serum creatinine ≤ 1.5 x ULN ii. Glomerular Filtration Rate (GFR) ≥ 30 ml/min/1.73m2 according to the Modified Diet in Renal Disease (MDRD) abbreviated formula iii. 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

• d. Coagulation: International Normalized Ratio (INR)/Partial Thromboplastin Time (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;

• e. Pancreatic function: Lipase ≤ 1.5 x ULN

• I9. Recovery to anticancer-treatment related 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);

• I10. Women of childbearing potential and male patients must agree to use adequate contraception (including at least the use of condoms) for the duration of treatment and for 7 months (210 days) in women of childbearing potential or 4 months (120 days) in men sexually active with women of childbearing potential after the last dose of regorafenib

• I11. 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;

• I12. Patients must be willing and able to comply with scheduled visits, treatment plan, laboratory tests and other study procedures;

• I13. Patients affiliated to the Social Security System

• I14. Body Surface Area (BSA) ≥ 1.30m² at the time of consenting to the study