- For the first 3-5 days (depending on the group), participants will be treated on an outpatient basis in the infusion room at the Dana-Farber Clinic, with fludarabine and rituximab. Fludarabine is given intravenously for 3-5 days. Rituximab is given intravenously on day 1 of each 28-day cycle. Lenalidomide is given orally once per day for 3 weeks, followed by 1 week of rest.