The purpose of this study is to:

Find out how safe and effective (by monitoring the good and/or bad effects) treatment with high dose temozolomide, thiotepa and carboplatin with stem cell rescue followed by 13-cis-retinoic acid has on children and adolescents with recurrent/refractory brain tumors

Find out how the body uses 13-cis-retinoic acid by studying the your blood levels and proteins in the blood that break down the 13-cis-retinoic acid

Determine how well 13-cis-retinoic acid penetrates into the spinal fluid.

Researchers have used high doses of combination chemotherapy followed by a stem cell rescue to treat recurrent brain tumors with moderate success. High dose chemotherapy with stem cell rescue has resulted in long term survival of about 25% in patients with several different types of recurrent brain tumors. Stem cells are cells in the bone marrow that produce blood cells. The stem cells are collected from the blood of the patient before the high dose chemotherapy. Patients are given high doses of chemotherapy to kill every brain tumor cell, but in the process the cells of the bone marrow are also killed. The previously collected stem cells are then infused into the patient to rescue the bone marrow and allow for healthy blood cells to re-populate and grow in the bone marrow. Initial studies used the drug etoposide along with carboplatin and thiotepa for the high dose chemotherapy. Patients had severe side effects, especially severe mouth-sores, thought mainly due to the etoposide, and some patients died from these side effects.

Recent studies have shown that a new drug, temozolomide, is active against some types of brain tumors. When it was given as a single drug to children with solid tumors, the side effects were considered to be tolerable. Temozolomide is given by mouth. In this study, researchers want to give high dose chemotherapy that includes the drugs temozolomide in place of etoposide, along with thiotepa and carboplatin. Patients will then be given their own stem cells back to rescue the bone marrow from the chemotherapy. A preliminary trial using this new drug combination was performed and has shown that patients tolerate this drug combination, even at the very high doses that will be used in this protocol.

Another drug that is being used in pediatric cancer treatment is called 13-cis-retinoic acid. This drug is closely related to vitamin A. It is taken by mouth. Cancer cells are immature cells that have not "grown up" into adult cells that do work in the body. 13-cis-retinoic acid is thought to act on some types of cancer cells to make them mature into cells that function in the body. It has also been shown in the laboratory to cause some brain tumor cells to undergo apoptosis. It has been used in other types of pediatric cancers and research is just beginning to use it for treatment of recurrent brain tumors. In this study researchers want to give you 13-cis-retinoic acid for 6 months after you recover from the high dose chemotherapy with stem cell rescue.

Inclusion Criteria:

1. Patients with recurrent or refractory medulloblastoma/PNET, CNS germ cell tumors, ependymomas, AT/RT, high grade glioma and other malignant brain tumors. Brainstem gliomas are eligible if residual disease is < 1.5cc and if the patient is off decadron.
2. Patients must have recurrent or refractory disease following at least one prior course of therapy and must have minimal residual disease defined as < 1.5 cm2 of enhancement. Patients with + CSF cytology, linear or fine nodular leptomeningeal disease are eligible.
3. Adequate hematologic, renal, liver, and cardiac function as demonstrated by laboratory values performed within 21 days, inclusive, prior to administration of temozolomide.
4. Patients must have an adequate number of autologous stem cells available defined as a minimum of 2 x 106 CD 34+ cells/kg and preferably at least 5 x 106 CD 34+ cells/kg.

Exclusion Criteria:

1. Previous myeloablative therapy
2. Frequent vomiting or medical condition that could interfere with oral medication intake (e.g., partial bowel obstruction)
3. Previous or concurrent malignancies at other sites with the exception of surgically cured carcinoma in-situ of the cervix and basal or squamous cell carcinoma of the skin. Patients with prior malignancies which have not required anti-tumor treatment within the preceding 24 months are eligible.