Bortezomib, dexamethasone, and high-dose melphalan as conditioning for stem cell transplantation in young Japanese multiple myeloma patients: a pilot study.

Autologous stem cell transplantation is recommended for younger patients with newly diagnosed multiple myeloma because of a high complete response rate and better survival. Bortezomib shows a synergistic effect with melphalan and has no prolonged hematologic toxicity, and the complete response rate after autologous stem cell transplantation is improved by combining bortezomib with melphalan for conditioning. Twelve patients were enrolled in a phase 2 study between February and November 2010, receiving bortezomib (1 mg/m(2) × 4), dexamethasone (20 mg/body × 8), and melphalan (200 mg/m(2)) for conditioning. No toxic deaths occurred. Neutrophils (absolute neutrophil count ≥0.5 × 10(9)/L) and platelets (≥20 × 10(9)/L without transfusion) recovered after a median of 5 days (range: 4-6 days) and 7 days (range: 4-8 days), respectively. No patient was admitted for exacerbation of peripheral neuropathy. Four patients obtained a stringent complete response, three patients obtained a complete response, and three patients showed a very good partial response. These results suggest that this conditioning regimen is safe and promising for young Japanese multiple myeloma patients. A prospective multicenter trial of this regimen combined with suitable induction and consolidation therapy should be performed.