- Regimen B: Three weeks after starting regimen A, patients receive high-dose cyclophosphamide IV over 24 hours on day 1. Patients without initial bone marrow involvement receive filgrastim (G-CSF) subcutaneously (SC) daily beginning on day 3 and continuing until autologous peripheral blood stem cells (PBSC) are harvested. PBSC are harvested on days 13-15 or when blood counts recover. Patients with initial bone marrow involvement do not undergo harvest of PBSC at this time, but receive G-CSF SC daily.