Intravenous busulfan and melphalan as a conditioning regimen for autologous stem cell transplantation in patients with newly diagnosed multiple myeloma: a matched comparison to a melphalan-only approach

Melphalan 200 mg/m(2) (MEL200) is the standard conditioning regimen administered to newly diagnosed patients with multiple myeloma (MM) undergoing autologous stem cell transplantation (ASCT). Few alternatives have been explored in order to improve the antimyeloma activity of this conditioning. We compare i.v. busulfan (BU) 9.6 mg/kg and MEL 140 mg/m(2) (MEL140) versus MEL200 mg/m(2) as a conditioning regimen before ASCT for newly diagnosed patients with MM. For this purpose, 51 patients receiving i.v. BU plus MEL were compared to 102 patients receiving MEL200 mg/m(2) in a 1:2 matched control analysis. Matching criteria included age, clinical stage at diagnosis, and response to induction therapy. No differences in the overall and complete response (CR) rates were observed after ASCT between both groups. After a median follow-up of 63 and 50 months in control and BU plus MEL groups, progression-free survival (PFS) was 24 and 33 months, respectively (P = .10). Most frequent toxicities included mucositis and febrile neutropenia in both groups. No case of sinusoidal obstruction syndrome was observed. Transplant-related mortality was 4% and 2% in BU plus MEL and control groups, respectively. ASCT conditioned with i.v. BU plus MEL may be considered an effective and well-tolerated alternative to a MEL-only approach as a conditioning regimen for patients with MM who are candidates for ASCT.