Inclusion Criteria

DISEASE CHARACTERISTICS:

- Diagnosis of multiple myeloma

- Relapsed or refractory disease, meeting 1 of the following criteria:

- Recurrent disease after stem cell transplantation

- Recurrent or progressive disease despite treatment with ≥ 1 standard
regimen (e.g., an alkylating agent plus glucocorticoid and/or the
combination of vincristine, doxorubicin hydrochloride, and dexamethasone)

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

- Monoclonal protein ≥ 1.0 g by serum 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)

- Patients must have already undergone hematopoietic stem cell collection, if believed
to be a transplant candidate OR not eligible for a hematopoietic stem cell transplant

PATIENT CHARACTERISTICS:

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

- ANC ≥ 1,000/mm^3

- Platelet count ≥ 75,000/mm^3

- Hemoglobin ≥ 8.0 g/dL (transfusions allowed)

- 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 active malignancy except for nonmelanoma skin cancer or carcinoma in situ of the
cervix or breast

- No uncontrolled infection

- No other co-morbidity that would interfere with the patient's ability to participate
in this trial

- No known hypersensitivity to any of the components of samarium Sm 153 lexidronam
pentasodium or bisphosphonates

PRIOR CONCURRENT THERAPY:

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

- More than 4 weeks since prior melphalan or other myelosuppressive agents

- More than 2 weeks since prior nonmyelosuppressive agents (e.g., thalidomide or
high-dose corticosteroids)

- More than 30 days since prior and no other concurrent investigational therapy

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

- No concurrent external beam radiotherapy

- No concurrent high-dose corticosteroids

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

- Low-dose steroids allowed for replacement or inhalation therapy

- No other concurrent medications, including any of the following:

- Cytotoxic chemotherapy

- Systemic antineoplastic therapy including, but not limited to, immunotherapy,
hormonal therapy, or monoclonal antibody therapy

- Prophylactic hematopoietic growth factors

- Hematopoietic growth factors allowed for established cytopenia therapy