This study is for patients that have been diagnosed with relapsed/refractory neuroblastoma. The investigational drug given is eflornithine (DFMO) along with etoposide. DFMO is the investigational drug being used along with etoposide for treatment of neuroblastoma. Participants will undergo a number of standard tests and research-related procedures before being able to enroll in this study. Some risks include but are not limited to: fewer red and white blood cells, diarrhea, abdominal pain, loss of appetite, skin rash, seizure, difficulty swallowing and blurred vision. Participants can expect to be on this study for approximately 2 years. Participants will then be followed for up to 5 years after study completion.

This study is for men and women with recurrent glioblastoma. The purpose of the study is to see if adding immune therapy drugs to usual radiation therapy can shrink or stabilize brain cancer.

This study is for newly diagnosed previously untreated neurofibromatosis type 1 (NF1) associated with low-grade glioma (LGG). The purpose of this study is to see if selumetinib works just as well as the standard treatment of carboplatin/vincristine (CV) for subjects with NF1-associated LGG, and to see if selumetinib is better than CV in improving vision in subjects with LGG of the optic pathway. Participants can expect to receive treatment for up to 24 months, until the cancer gets worse or until the side effects are too great. After study completion, participants will continue to be followed for up to 10 years.

This study is for newly diagnosed or previously untreated low-grade glioma (LGG). The overall goal of this study is to see if selumetinib works just as well as the standard treatment using carboplatin and vincristine (called CV) for subjects with LGG. Selumetinib is a drug that works by blocking a protein (a basic building block of the human body) that lets cancer cells grow without stopping. Participants can expect to receive treatment on this study for about 1–2 years. After study completion, participants will continue to be followed for up to 10 years.

This study is for participants that have been diagnosed with Medulloblastoma. The purpose of this study is to test the effectiveness of using an investigational agent called DFMO for Medulloblastoma. An investigational drug is one that has not been approved by the U.S. Food and Drug Administration (FDA). This study will look at the ability of this study drug to either keep participants tumor in remission or if they have active tumor, for their tumor to respond to the treatment and will also look at the safety and tolerability of DFMO. After this first day participants will be seen in clinic once every 30 days for the first 6 months of the study, after that they will be seen once every 90 days for the remainder of the study. These visits will last about 2 hours.