- Stem cell mobilization and in vivo purging: Beginning 8-10 weeks after the first day of the last course of remission induction or CHOP, patients receive rituximab IV on days 1 and 8, cyclophosphamide IV over 4 hours on day 2, and filgrastim (G-CSF) SC daily beginning on day 4 and continuing until the last day of apheresis. Patients undergo apheresis on days 11-14.