This non-therapeutic study was registered in error. The PRS team doesn't delete studies once registered, so they recommended changing the status to Withdrawn

RATIONALE: Studying samples of blood in the laboratory from patients receiving radiation therapy and chemotherapy may help doctors learn more about the effects of this treatment on cells. It may also help doctors understand how well patients respond to treatment.

PURPOSE: This research study is studying biomarkers in blood samples from young patients with newly diagnosed brain tumors undergoing standard radiation therapy and chemotherapy.

OBJECTIVES:

Primary

• Evaluate the fraction of peripherally circulating T-regulatory cells (T_regs) in pediatric patients with newly diagnosed medulloblastoma and compare it to the levels found in a control group of patients undergoing craniectomy for Chiari malformation.
• Evaluate the longitudinal effects of standard radiotherapy and chemotherapy regimens on the overall population of lymphocytes as well as the fraction of T_reg cells in patients with medulloblastoma.

Secondary

• Determine the baseline fraction of T_reg cells in those with non-medulloblastoma posterior fossa tumors compared to levels found in patients undergoing decompression for Chiari malformation.

OUTLINE: This is a multicenter study.

Patients with Chiari malformation and patients with posterior fossa tumor undergo standard surgery. Patients with posterior fossa tumor also receive standard radiotherapy and chemotherapy.

Blood samples are collected at baseline and periodically to measure the level of circulating T-regulatory cells.

DISEASE CHARACTERISTICS:

• Meets 1 of the following criteria:

  • Histologically confirmed posterior fossa tumor

    • Newly diagnosed disease
    • Medulloblastoma OR non-medulloblastoma (pilocytic astrocytoma, ependymoma, atypical rhabdoid tumor, or others)
    • Scheduled to undergo craniotomy and tumor resection

  • Chiari malformation

    • Requires craniectomy for decompression

      • No secondary decompression

PATIENT CHARACTERISTICS:

• No unexplained febrile illness
• No active infection
• No autoimmune disorders such as inflammatory bowel disease, juvenile rheumatoid arthritis, or systemic lupus erythematosus
• No other immunosuppressive disorders (e.g., HIV infection)

PRIOR CONCURRENT THERAPY:

• See Disease Characteristics