Patients receive conditioning chemotherapy consisting of oral busulfan every 6 hours on days -7, -6, -5, and -4 for a total of 14 doses and cyclophosphamide IV over 1 hour on days -3 and -2. Patients undergo autologous stem cell infusion on day 0. G-CSF is administered IV or SC daily beginning on day 1 and continuing until blood counts recover.