Treatment

All patients received induction with VRD, which consisted of bortezomib 1.3 mg/m² (subcutaneous) on days 1, 4, 8, and 11 of each cycle; lenalidomide 25 mg/d on days 1 to 21; and dexamethasone 40 mg on days 1 to 4 and 9 to 12 at 4-week intervals for 6 cycles. Mobilization was performed after the third induction cycle in the absence of progression or unacceptable toxicity. The minimum number of CD34-positive cells was determined at the discretion of each site, although ≥2 × 10⁶/kg was recommended. Patients next received conditioning with IV busulfan 9.6 mg/kg + melphalan 140 mg/m² vs melphalan 200 mg/m², as previously described,³³ with the notable exception that busulfan 3.2 mg/kg was administered by a 3-hour infusion on days −5, −4, and −3 (total accumulated dose, 9.6 mg/kg) and consolidation with 2 additional cycles of VRD 3 months after ASCT. Thromboprophylaxis with low-molecular-weight heparin was mandatory. Antiviral prophylaxis was also required. Antibacterial prophylaxis was administered at each site’s discretion.