Busulfan plus melphalan versus melphalan alone conditioning regimen after bortezomib based triplet induction chemotherapy for patients with newly diagnosed multiple myeloma

BACKGROUND: High dose melphalan (HDMEL) is considered the standard conditioning regimen for autologous stem cell transplantation (ASCT) in multiple myeloma (MM) patients. Recent studies showed superiority of busulfan plus melphalan (BUMEL) compared to HDMEL as a conditioning regimen. We compared the efficacy of HDMEL and BUMEL in newly diagnosed Asian MM patients, who are often underrepresented. METHODS: This is a single-center, retrospective study including MM patients who underwent ASCT after bortezomib-thalidomide-dexamethasone (VTD) triplet induction chemotherapy between January 2015 and August 2019. RESULT: In the end, 79 patients in the HDMEL group were compared to 31 patients in the BUMEL group. There were no differences between the two groups with regards to sex, age at ASCT, risk group, and stage. The HDMEL group showed better response to pre-transplant VTD compared to BUMEL, but after ASCT the BUMEL group showed better overall response. In terms of progression-free survival (PFS), although BUMEL showed trends towards better PFS regardless of pre-transplant status and age, the difference did not reach statistical significance. The BUMEL group more often experienced mucositis related to chemotherapy, but there was no difference between the two groups with regards to hospitalization days, cell engraftment, and infection rates. CONCLUSION: BUMEL conditioning deserves attention as the alternative option to HDMEL for newly diagnosed MM patients, even in the era of triplet induction chemotherapy. Specifically, patients achieving very good partial response (VGPR) or better response with triplet induction chemotherapy might benefit the most from BUMEL conditioning. Tailored conditioning regimen, based on patient’s response to induction chemotherapy and co-morbidities, can lead to better treatment outcomes.