Continuous Infusion Cyclophosphamide and Low-Dose Total Body Irradiation Is a Safe and Effective Conditioning Regimen for Autologous Transplant in Multiple Myeloma

We present the results of a novel conditioning regimen in multiple myeloma (MM) patients undergoing tandem autologous stem cell transplant (ASCT). MM patients were enrolled in a prospective phase II clinical trial. After initial ASCT, disease response was assessed by day +100. Patients achieving very good partial remission (VGPR) were offered maintenance therapy. If patients achieved VGPR, they were offered a second ASCT using continuous intravenous cyclophosphamide (CICy) 6 g/m2 over 4 days and low-dose total body irradiation (ldTBI) 600 rads over 2 days. Total body irradiation was replaced by melphalan 140 mg/m2 if patients had received prior radiation. Twenty-one patients received tandem ASCT. Three patients received CICy and melphalan. Median duration of neutropenia with CICy/ldTBI was 11 days. Fifteen patients (71.4%) developed febrile neutropenia while grade 1 to 2 diarrhea was the next most common adverse event (42.9%). There was no treatment-related mortality. Four patients had entered complete remission (19%) and 6 achieved VGPR (28.6%). In conclusion, this conditioning regimen is safe and effective and may be useful in patients who do not benefit from first ASCT using more traditional conditioning regimen.