One day after the first dose of rituximab (Day 2), fludarabine and cyclophosphamide will be given by IV every day for 3 days (Days 2, 3, and 4), and mitoxantrone will be given by IV on Day 2. Fludarabine and cyclophosphamide will be given as 30-minute infusions, while the infusion of mitoxantrone will take 30-60 minutes. After the first treatment cycle, all the drugs will be given on Days 1, 2, and 3 for every cycle after that. Pegfilgrastim will be given as a subcutaneous injection (an injection under the skin) once per treatment cycle, right after you receive the last chemotherapy drug (in other words, on Day 4 during the first cycle, and on Day 3 for every cycle after that). Other IV fluids, such as saline, will be given on all of the treatment days to keep you hydrated, which means that each clinic visit will take about 6 hours. The combination will be repeated once every 4 to 6 weeks for a total of 6 courses.