Childhood Posterior Fossa Ependymoma

This phase I/II trial tests the safety, side effects best dose and how well giving fluorouracil and tretinoin along with standard of care radiation therapy works for the treatment of high risk posterior fossa ependymoma that has not spread to other parts of the body (localized). Fluorouracil is a type medication called an antimetabolite. It works by stopping cells from making DNA and it may kill tumor cells. Tretinoin, also called all-trans retinoic acid (ATRA), retinoic acid, and vitamin A acid is in a class of medications called retinoids. It is made in the body from vitamin A and helps cells to grow and develop, especially in the embryo. Laboratory made form of tretinoin works by slowing or stopping the growth of tumor cells. Radiation therapy uses high energy x-rays, particles, or radioactive seeds to kill tumor cells and shrink tumors. Giving fluorouracil and tretinoin along with standard of care radiation therapy may be safe, tolerable and/or effective in treating patients with localized high risk posterior fossa ependymoma.