Busulfan plus melphalan versus high-dose melphalan as conditioning regimens in autologous stem cell transplantation for newly diagnosed multiple myeloma.

Background: High-dose melphalan (HDMEL) represents the standard conditioning regimen before autologous stem cell transplant (ASCT) in multiple myeloma (MM), but recent updates have suggested combination of melphalan with bulsulfan (BUMEL) is also associated with favorable outcomes. We performed the current study to address the lack of comparative studies between the two conditioning regimens in Asian populations.

Methods: Using the Korean National Health Insurance and Korean Health Insurance Review and Assessment Service databases, 1,304 patients newly diagnosed with MM undergoing ASCT between January 2010 and December 2014 were identified. Patients were divided according to conditioning regimen (HDMEL vs. BUMEL), and after case matching, 428 patients undergoing HDMEL conditioning were compared to 107 patients undergoing BUMEL conditioning with respect to clinical course and treatment outcomes.

Results: The 3-year progression-free survival (PFS) was 52.5% for the HDMEL conditioning group versus 70.3% for the BUMEL conditioning group ( P =0.043). The 3-year overall survival (OS) was 82.0% versus 83.5% ( P =0.525), respectively. Although not statistically significant, BUMEL conditioning was associated with more platelet transfusion, while HDMEL was associated with more granulocyte colony stimulating factor support. In multivariate analysis, BUMEL conditioning was not inferior to HDMEL conditioning in regard to both PFS and OS.

Conclusion: Our study confirmed that BUMEL is an effective and well-tolerated alternative to HDMEL conditioning, with better PFS.