The purpose of this phase II study is to assess the toxicity and efficacy of sequentially administered high dose chemotherapy followed by autologous stem cell rescue in the treatment of multiple myeloma. Multiple myeloma is a chemotherapy sensitive disease but is not curative with standard therapy with a median survival of 2 to 4 years. Prior studies have shown that dose-intensified melphalan can produce higher response rates and complete remission in some patients. Over the past several years, multiple phase II studies utilizing high dose chemotherapy or high dose chemo-radiotherapy with autologous marrow or peripheral blood stem cell rescue have demonstrated improved response rates and survival rates compared to historical controls. Recently a prospective randomized trial has demonstrated improved response rates, response duration and overall survival utilizing high dose therapy with autologous bone marrow support compared to standard chemotherapy. The primary cause of failure is relapse and it is unclear how many, if any, patients are cured by this approach. Based on observations of efficacy in Hodgkin's Disease, Non-Hodgkin's Lymphoma, and breast cancer, an approach utilizing sequential high dose chemotherapy in multiple myeloma was developed. This protocol tests the sequential regimen in multiple myeloma patients who have responded to a standard dose chemotherapy regimen prior to enrollment. As originally written, eligible patients were required to have sensitive disease.

The protocol was revised in August 1998 to allow entry of patients with newly diagnosed myeloma who had stable but not progressive disease following VAD chemotherapy. Patients with recurrent myeloma were still required to have chemotherapy sensitive disease. Eligible patients must also have pathologically confirmed multiple myeloma, no prior bone marrow transplantation and acceptable organ function (pulmonary, renal, hepatic, and cardiac). The recent revision of the protocol also allows entry of patients with renal insufficiency due to multiple myeloma to be enrolled on the protocol. Prior to initiating high dose therapy, patients must undergo a complete history and physical exam with routine lab work plus titers for HIV, CMV, HSV, and VCV: immunoglobulin levels, beta-2 microglobulin and serum protein electrophoresis as well as immunoelectrophoresis and bone marrow aspirates and biopsies. These studies are all standard for multiple myeloma patients. All patients require a double Human Hickman to be placed prior to the start of therapy. The protocol was originally written to include total body irradiation and high dose Melphalan as a preparative regimen for patients who had not received prior radiotherapy. Patients who were not eligible for TBI received high dose BCNU plus Melphalan. A revision removed the TBI Melphalan arm from the protocol after analysis of over 100 patients treated at Stanford University Medical Center on this same protocol showed no difference in event-free survival or overall survival between the TBI containing arm and the chemotherapy only preparative regimen. The TBI arm was dropped due to the increased cost and morbidity of TBI and the associated scheduling and logistics problems. The other revision to the protocol was the inclusion of CD34 stem cell selection on the stem cells collected by leukapheresis following high dose cyclophosphamide. This change was based on the results of a Phase III study which demonstrated that the degree of tumor cell contamination of these stem cell collections could be decreased by 3-6 logs with CD34 cell selection. The dose of Melphalan was also increased to 200 mg/m2 after completion of a dose escalation study at Stanford.