TREATMENT OF CHILDREN AND YOUNG ADULTS WITH RECURRENT/REFRACTORY SOLID TUMORS WITH HIGH DOSE ETOPOSIDE AND CARBOPLATIN PLUS ESCALATING DOSE CYCLOPHOSPHAMIDE, FOLLOWED BY HEMATOPOIETIC RESCUE USING AUTOLOGOUS CD34+ SELECTED BLOOD STEM CELLS: A PILOT STUDY

OBJECTIVES:

• Determine whether autologous transplantation of mobilized CD34+ peripheral blood stem cells (PBSC) can provide complete hematologic reconstitution after myeloablative chemotherapy comprising etoposide (VP-16) and carboplatin (CBDCA) in patients with metastatic or recurrent rhabdomyosarcoma, neuroblastoma, Ewing's sarcoma/primitive neuroectodermal tumor, germ cell tumors, childhood brain tumors, or hepatoblastoma.
• Determine the frequency and yield of CD34+ PBSC and granulocyte-macrophage colony-forming units (GM-CFU) that are mobilized, harvested, and purified after a single priming course of high-dose cyclophosphamide (CTX) followed by filgrastim (G-CSF).
• Correlate the number of CD34+ cells and GM-CFU in the autologous PBSC graft with time to engraftment of white blood cells, neutrophils, and platelets in these patients.
• Determine the optimal day of PBSC harvest after a single priming course of high-dose CTX and G-CSF in these patients.
• Determine whether CD34+ PBSC rescue and daily post-transplantation G-CSF decrease the time to hematopoietic recovery after high-dose VP-16 and CBDCA compared to historical results achieved in similar patients rescued with bone marrow.
• Compare the tumor cell content of marrow, mobilized blood, and purified CD34+ PBSC graft preparations.
• Determine the optimal timing of PBSC mobilization and harvest in relation to extent of prior chemotherapy in these patients.
• Determine the feasibility of a single leukapheresis for PBSC harvest in children.
• Determine the toxic effects of this regimen in these patients.
• Determine the antitumor activity of this regimen in these patients.

OUTLINE: This is a dose-escalation study of cyclophosphamide.

Mobilization/harvest: Patients receive cyclophosphamide IV over 90 minutes on day 0 and filgrastim (G-CSF) subcutaneously or IV over 30 minutes on days 2-15 or until blood counts recover. Peripheral blood stem cells (PBSC) are harvested and selected for CD34+ cells on day 15. Bone marrow is also harvested in case insufficient PBSC are harvested.

Preparative regimen/transplantation: Patients receive carboplatin IV over 1 hour and etoposide IV continuously on days -6 to -4. Cyclophosphamide is administered IV over 1 hour on days -3 and -2 or IV continuously on days -3 and -2, -4 to -2, -5 to -2, or -6 to -2. PBSC or bone marrow is reinfused on day 0.