This study is for children and young adults with a brain tumor called NGGCT. NGGCT stands for non-germinomatous germ cell tumors. These tumors are in the brain but haven't spread to other parts of the body. The study aims to find the best way to combine chemotherapy and radiation therapy based on how patients respond to initial treatment. Chemotherapy uses drugs to kill cancer cells or stop them from growing, while radiation therapy uses high-energy rays to do the same. The study will help decide if patients need more chemotherapy, radiation, or both, depending on how their tumors react to the first treatment.

Key Points:

• **Study Length**: Patients will be followed for up to 10 years after treatment.
• **Treatment**: Includes chemotherapy and possibly radiation therapy or a stem cell transplant.
• **Eligibility**: Patients aged 3 to 30 with specific types of brain tumors can join.

After initial chemotherapy, patients may receive different treatments based on their tumor response. This personalized approach aims to reduce side effects and improve outcomes.