PRIOR CONCURRENT THERAPY: Biologic therapy: No concurrent stem cell transplant Chemotherapy: See Disease Characteristics At least 14 days since prior chemotherapy and recovered (unless evidence of disease progression) No concurrent chemotherapy No prior arsenic treatment Endocrine therapy: No concurrent steroidal or hormonal therapy for cancer Steroids for adrenal failures and hormones for nondisease conditions allowed Radiotherapy: At least 14 days since prior radiotherapy and recovered (unless evidence of disease progression) No concurrent radiotherapy Other: At least 14 days since other investigational agents and recovered (unless evidence of disease progression) No concurrent other investigational agents