INTER-EWING-1 is a large international trial for children and young adults newly diagnosed with Ewing Sarcoma, a rare bone and soft tissue cancer. The study aims to find a more effective treatment by testing three specific changes: adding a new targeted drug called regorafenib to chemotherapy, refining radiation therapy doses, and testing if extra chemotherapy at the end of treatment prevents the cancer from coming back. By evaluating these different approaches, researchers hope to increase survival rates and improve the long term health of young survivors by finding the most effective balance of treatments.