Patients receive high-dose melphalan IV on day -1. PBSCs are reinfused on day 0. G-CSF is administered IV or SC daily beginning on day 1 and continuing until blood counts recover. Between 8 and 14 weeks later, patients receive high-dose busulfan IV every 6 hours on days -7 to -4 and cyclophosphamide IV over 2 hours on days -3 and -2. PBSCs are reinfused on day 0 and G-CSF is administered IV or SC daily until blood counts recover.