A Phase 2 Study of Bendamustine Plus Melphalan Conditioning for Second Autologous Stem Cell Transplantation in "De-Novo" Multiple Myeloma Patients in a Tandem Transplant Strategy

Background:

High-dose melphalan (HDM) is the standard therapy for autologous stem cell transplantation (ASCT) in multiple myeloma (MM), although the optimal conditioning regimen remains yet to be identified. Bendamustine (BENDA) has a proved activity in hematological malignancies including both first line and relapsed MM.

Methods:

We conducted a phase II trial, adding BENDA to HDM before second ASCT, in a tandem ASCT strategy, in 32 patients with "de-novo" MM. All patients received a bortezomib-based induction therapy. High-dose cyclophosphamide (CY) and G-CSF were used to mobilize stem cells. Four to 6 weeks after the administration of CY, patients received HDM (200 mg/mq), followed by ASCT. Three to 6 months after the first transplantation, patients received a second ASCT with BENDA (200 mg/m2) to HDM (140 mg/m2) as conditioning regimen (BM).

Results: The median age was 56 years (range 40 to 66). Overall, there was no transplant related mortality. The incidence of neutropenic fever and mucositis (grade 1-2) was 46.9% and 81.2%, respectively. No mucositis grade 3-4 was observed. Median number of days to neutrophil and platelet engraftment were 11 and 12, respectively. After the second transplantation, the complete response (CR) improved to 62.5%. Overall response rate was 90.6%. After a median follow-up of 18,2 months, 4 patients had progressed and 1 died. Median progression free survival (PFS) was not reached and actuarial 2-year PFS and OS was 78% and 90%, respectively.

Conclusion: Bendamustine plus melphalan is feasible as conditioning regimen for second ASCT in MM and should be explored for efficacy in a phase III study. Longer follow-up is needed to evaluate conversion rate and survival.