Inclusion Criteria

DISEASE CHARACTERISTICS:

- Diagnosis of multiple myeloma

- Relapsed or refractory disease

- Measurable or evaluable disease as defined by at least 1 of the following:

- Serum monoclonal protein ≥ 1.0 g by protein electrophoresis

- Monoclonal protein ≥ 200 mg by 24-hour urine electrophoresis

- Serum immunoglobulin free light chain ≥ 10 mg/dL AND abnormal serum
immunoglobulin kappa to lambda free light chain ratio

- Monoclonal bone marrow plasmacytosis ≥ 30% (evaluable disease)

- Previously treated disease

- No limit to prior therapy provided there is adequate residual organ function

- Must have undergone hematopoietic stem cell collection (for transplant candidates) OR
not considered to be a hematopoietic stem cell transplant candidate

PATIENT CHARACTERISTICS:

- ECOG performance status (PS) 0-2 (ECOG PS of 3 allowed if secondary only to pain)

- Platelet count ≥ 75,000/mm^3

- Hemoglobin ≥ 8.0 g/dL (transfusion allowed)

- ANC ≥ 1,000/mm^3

- Creatinine ≤ 3 mg/dL

- Calcium ≤ 15 mg/dL

- Not pregnant or nursing

- Negative pregnancy test

- Fertile patients must use effective contraception during and for 4 weeks after
completion of study therapy

- No impending long bone fracture

- No other active malignancy except nonmelanoma skin cancer, carcinoma in situ of the
cervix, or breast cancer

- No uncontrolled infection

- No known hypersensitivity to any of the components of study drugs

- No other co-morbidity that would preclude study participation

PRIOR CONCURRENT THERAPY:

- Recovered from prior surgery, radiotherapy, or other antineoplastic therapy

- No prior samarium Sm 153 lexidronam pentasodium or strontium chloride Sr 89

- At least 3 weeks since prior myelosuppressive agents

- At least 2 weeks since prior nonmyelosuppressive agents (e.g., thalidomide)

- At least 2 weeks since prior and no concurrent high-dose corticosteroids

- Chronic steroids (maximum dose of 20 mg/day prednisone or equivalent) allowed
for disorders other than myeloma (i.e., adrenal insufficiency or rheumatoid
arthritis)

- At least 30 days since prior and no other concurrent investigational therapy

- No concurrent external beam radiotherapy

- No concurrent cytotoxic chemotherapy

- No other concurrent systemic antineoplastic therapy including, but not limited to,
any of the following:

- Immunotherapy

- Hormonal therapy

- Monoclonal antibody therapy