Intravenous busulfan plus melphalan versus melphalan alone as conditioning regimen for patients with multiple myeloma

Abstract

Dear Editor, To improve results in transplant-eligible multiple myeloma (MM) patients, the combination of busulfan and melphalan (BUMEL) has been used as an alternative conditioning regimen to standard-dose melphalan 200 mg/m (MEL200) [1–4]. The results of a matched case-control study comparing the outcome of a series of patients with newly diagnosed MM (NDMM) receiving induction with conventional chemotherapy followed by autologous stem cell transplantation (ASCT) after conditioning with BUMEL (n = 51) or MEL200 (n = 102) was previously reported [5]. Initial results showed a 6-year progressionfree survival (PFS) of 23% in the BUMEL and 17% in the control group (P = 0.1). However, the preceding Spanish experience [6], which suggested that long-term follow-up analyses should be mandatory when considering the antimyeloma effect of a conditioning regimen, prompted us to update our results. After a median follow-up of 56 and 63 months, median PFS was 33 and 24 months in the BUMEL and control groups, respectively (P = .04; Fig. 1). Interestingly, 12 patients in the BUMEL group maintained their response, and in fact, ten of them sustained their response for more than 9 years after transplantation and no long-term side effects have been observed to date. The median OS was 65.7 and 65.1 months in the BUMEL group and the control group, respectively. Recently, Jung et al. have reported the results of ASCT after conditioning with BUMEL in 99 patients with MM [7]. The overall response (OR) and complete response (CR) rates were 94% and 43.5%, respectively. There was no transplant-related mortality, and after a median follow-up of 26.1 months, the median PFS was 27.2 months. Overall, our results compare favourably with those observed by Jung et al., although in our study no patient received new drugs in induction or maintenance therapy and no consolidation was administered after transplant. Furthermore, we have also reported the results of 47 NDMM patients undergoing ASCT with BUMEL after a bortezomib-based induction, an approach similar to the one reported by Jung et al. [8] with an OR and CR after transplant of 100% and 49%, respectively. Finally, with a median follow-up of 24.5 months, median PFS was not reached. Conversely to our studies, including only patients with newly diagnosed MM, in the Korean study, some of the patients received more than one line of induction therapy and patients proceeding to ASCT within 12 months of initial diagnosis had better PFS than those who underwent late ASCT (27.2 versus 14.6 months; P = .099).