Total-Body Irradiation, Thiotepa, and Fludarabine in Treating Young Patients Who Are Undergoing a Donor Stem Cell Transplant for Hematologic Cancer

OBJECTIVES: Primary * Determine the safety of a conditioning regimen without anti-thymocyte globulin comprising total body irradiation, thiotepa, and fludarabine followed by CD34-positive-selected haploidentical allogeneic peripheral blood stem cell transplantation in young patients with life-threatening hematologic malignancies. Secondary * Determine the risk for severe graft-vs-host disease in patients treated with this regimen. * Determine the kinetics of immune reconstitution in patients treated with this regimen. * Determine the risk for life-threatening infections in patients treated with this regimen. OUTLINE: * Conditioning regimen: Patients 7 years of age and under undergo total body irradiation twice daily on days -9 to -7. Patients over 7 years of age undergo total body irradiation once on day -7. All patients receive fludarabine IV once daily on days -6 to -2 and thiotepa IV over 2 hours twice on day -5. * CD34-positive (CD34+)-selected haploidentical allogeneic peripheral blood stem cell transplantation (PBSCT): Patients undergo CD34+-selected allogeneic PBSCT on days 0 and 2. Patients with acute lymphoblastic leukemia or CNS disease also receive methotrexate intrathecally twice before transplantation and 4 times after day 35 post-transplantation. Male patients with lymphoid malignancies undergo additional radiotherapy to the testes. After completion of study treatment, patients are followed for at least 100 days, at 1 year, and then periodically thereafter. PROJECTED ACCRUAL: A total of 20 patients (10 patients ≤ 7 years of age and 10 patients \> 7 years of age) will be accrued for this study within 3 years.