Combination Chemotherapy Followed by Bone Marrow or Peripheral Stem Cell Transplantation in Treating Patients With Multiple Myeloma

OBJECTIVES: I. Assess the toxicity and efficacy at the maximum tolerated dose of busulfan, melphalan, and thiotepa in patients with multiple myeloma. OUTLINE: This is a single arm, open label study. Peripheral blood stem cells (PBSC) are collected and cryopreserved, or bone marrow is harvested and stored, until infusion on day 0. Patients receive oral busulfan every 6 hours on days -8, -7, and -6. Melphalan is administered by continuous IV infusion over 30 minutes on days -5 and -4. Thiotepa is administered by continuous IV infusion over 2 hours on days -3 and -2. Patients undergo PBSC or bone marrow infusion 36-48 hours following the completion of chemotherapy (day 0). Patients are followed for 100 days posttransplant and every 3 months thereafter. PROJECTED ACCRUAL: 30 patients will be accrued.