Arsenic Trioxide and Dexamethasone in Treating Patients With Recurrent or Refractory Stage II or Stage III Multiple Myeloma

DISEASE CHARACTERISTICS: Diagnosis of stage II or III multiple myeloma Refractory myeloma defined as progressive disease (more than 25% increase in M protein or in radiographic findings of nonsecretory myeloma) despite up to 3 courses of prior cytotoxic chemotherapy No more than 3 prior cytotoxic regimens No more than 1 prior high-dose cytotoxic regimen with stem cell transplantation History of disease progression after prior steroid antimyeloma therapy No smoldering myeloma Measurable disease based on presence of serum and urine M protein and/or measurable plasmacytoma PATIENT CHARACTERISTICS: Age: Over 18 Performance status: Karnofsky 70-100% Life expectancy: At least 3 months Hematopoietic: Absolute granulocyte count greater than 1,200/mm^3* Platelet count greater than 75,000/mm^3* Hemoglobin greater than 10 g/dL* NOTE: *Unless due to multiple myeloma Hepatic: Bilirubin no greater than 2 times upper limit of normal (ULN) SGOT and SGPT no greater than 2 times ULN Renal: Creatinine no greater than 1.5 times ULN Cardiovascular: Absolute QT interval less than 460 msec in the presence of normal potassium and magnesium levels No significant underlying cardiac dysfunction No conduction defects No unstable angina No congestive heart failure No New York Heart Association class II-IV cardiac disease No myocardial infarction within the past 6 months Other: No preexisting grade 2 or greater neurotoxicity/neuropathy No other malignancy within the past 5 years except curatively treated carcinoma in situ of the cervix or nonmelanoma skin cancer No uncontrolled diabetes mellitus No active serious infection uncontrolled by antibiotics No history of grand mal seizures (other than infantile febrile seizures) Not pregnant or nursing Negative pregnancy test Fertile patients must use effective contraception PRIOR CONCURRENT THERAPY: Biologic therapy: See Disease Characteristics See Chemotherapy At least 28 days since prior biologic therapy Chemotherapy: See Disease Characteristics At least 28 days since prior cytotoxic chemotherapy, including high-dose cytotoxic regimen with stem cell transplantation No other concurrent cytotoxic chemotherapy Endocrine therapy: See Disease Characteristics Radiotherapy: At least 28 days since prior radiotherapy except for focal radiation for symptom control Surgery: Not specified