This study looks at how well cabozantinib in combination with MAP work when given to children and young adults with newly diagnosed OST disease. Cabozantinib is experimental because it has not been proven to work in a situation like yours and in combination with MAP. Cabozantinib has been approved for use in children ages 12 years and older with a certain type of thyroid cancer. It has also been tested in a study that used cabozantinib alone to treat children with various types of cancers including OST that has not responded to treatment or has returned after treatment (recurrent). The amount of cabozantinib given on that study is higher than the dose of cabozantinib you will get on this study because you will also get MAP alongside cabozantinib. Studies have found that cabozantinib was able to prevent new disease or decrease the size of the tumor in both adults and children with OST.