Busulfan 12 mg/kg plus melphalan 140 mg/m2 versus melphalan 200 mg/m2 as conditioning regimens for autologous transplantation in newly diagnosed multiple myeloma patients included in the PETHEMA/GEM2000 study

27 páginas, 3 figuras, 2 tablas.-- et al.Background The aim of this study was to compare the long-term safety and efficacy of oral busulfan 12 mg/kg plus melphalan 140 mg/m2 and melphalan 200 mg/m2 as conditioning regimens for autologous stem cell transplantation in newly diagnosed patients with multiple myeloma in the GEM2000 study. Design and Methods The first 225 patients received oral busulfan 12 mg/kg plus melphalan 140 mg/m2; because of a high frequency of veno-occlusive disease, the protocol was amended and a further 542 patients received melphalan 200 mg/m2. Results Engraftment and hospitalization times were similar in both groups. Oral busulfan 12 mg/kg plus melphalan 140 mg/m2 resulted in higher transplant-related mortality (8.4% versus 3.5%; P=0.002) due to the increased frequency of veno-occlusive disease in this group. Response rates were similar in both arms. With respective median follow-ups of 72 and 47 months, the median progression-free survival was significantly longer with busulfan plus melphalan (41 versus 31 months; P=0.009), although survival was similar to that in the melphalan 200 mg/m2 group. However, access to novel agents as salvage therapy after relapse/progression was significantly lower for patients receiving busulfan plus melphalan (43%) than for those receiving melphalan 200 mg/m2 (58%; P=0.01). Conclusions Conditioning with oral busulfan 12 mg/kg plus melphalan 140 mg/m2 was associated with longer progression-free survival but equivalent survival to that achieved with melphalan 200 mg/m2 but this should be counterbalanced against the higher frequency of veno-occlusive disease-related deaths. This latter fact together with the limited access to novel salvage therapies in patients conditioned with oral busulfan 12 mg/kg plus melphalan 140 mg/m2 may explain the absence of a survival difference. Oral busulfan was used in the present study; use of the intravenous formulation may reduce toxicity and result in greater efficacy, and warrants further investigation in myeloma patients.This research was supported by grant PI051284 from the Fondo de Investigación Sanitaria (FIS), Instituto Carlos III, Ministerio de Sanidad, by the Cooperative Research Thematic Network (G03/136 and RD06/0020/0006), and by the Instituto de Salud Carlos III/Subdirección General de Investigación Sanitaria (PI060339 and 02/0905).Peer reviewe