Patients receive denileukin diftitox IV over 20-80 minutes on days 1-3, 8, 15, 22, 29, 36, 43, 50, 57, 64, 71, 78, 85, 92, and 99 (weeks 1-16) in the absence of disease progression or unacceptable toxicity. Patients achieving a partial response at week 16 may continue treatment once monthly for up to 8 additional doses or until a complete response (CR) is achieved. Patients achieving a CR (at any time) receive 2 additional monthly doses of denileukin diftitox beyond CR.