Patients receive arsenic trioxide IV over 1-2 hours on days 1-5 of week 1 and on days 1 and 5 of weeks 2-8 (course 1 only). Beginning with course 2 and for all subsequent courses, patients receive arsenic trioxide on days 1 and 5 of weeks 1-8. Treatment repeats every 8 weeks for up to 6 courses in the absence of disease progression or unacceptable toxicity. Patients achieving complete response (CR) receive 1 additional course of therapy beyond CR. Patients achieving CR due to local consolidative therapy (surgery or radiotherapy) receive 2 additional courses of therapy beyond CR.