Patients receive recombinant human interleukin-21 (rIL-21) IV on days 1-5 of weeks 1, 3 and 5. Treatment repeats every 8 weeks in the absence of disease progression or unacceptable toxicity. Patients achieving a complete response (CR) or partial response (PR) receive 2 courses beyond CR or PR. Patients with stable disease receive a maximum of 3 courses of rIL-21.