• The proportion of confirmed response (complete response, partial response, or very good partial response) during first 4 months of treatment [ Designated as safety issue: No ]
  

• Overall survival [ Designated as safety issue: No ]
  
• Progression-free survival [ Designated as safety issue: No ]
  
• Duration of response [ Designated as safety issue: No ]
  

OBJECTIVES:

Primary

• To evaluate the hematological response rate of anti-thymocyte globulin given in combination with melphalan in patients with relapsed multiple myeloma.

Secondary

• To assess the toxicity and tolerability of this combination in these patients.
• To assess time to disease progression in patients treated with these drugs.
• To assess survival of patients treated with these drugs.

OUTLINE: Patients receive anti-thymocyte globulin IV over 6 hours and melphalan IV on day 1. Treatment repeats every 28 days for 6 courses. Patients then receive melphalan alone as above for another 6 courses. Treatment continues in the absence of disease progression or unacceptable toxicity.

After completion of study treatment, patients are followed every 3 months until disease progression and then every 6 months for up to 2 years.

DISEASE CHARACTERISTICS:

• Diagnosis of multiple myeloma

  • Relapsed disease
• Must not be a candidate for stem cell transplantation, has refused transplantation, or has had stem cells collected previously

• Measurable disease, defined by ≥ 1 of the following:

  • Serum monoclonal protein ≥ 1.0 g by protein electrophoresis
  • More than 200 mg of monoclonal protein in the urine on 24 hour 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)

PATIENT CHARACTERISTICS:

• ECOG performance status 0-3
• Absolute neutrophil count ≥ 1,000/μL
• Platelet count ≥ 75,000/μL
• Hemoglobin ≥ 8.0 g/dL
• CD4 > 100/μL
• Creatinine ≤ 3 mg/dL
• Not pregnant or nursing
• Negative pregnancy test
• Fertile patients must use effective contraception
• No active malignancy with the exception of nonmelanoma skin cancer or in situ cervical or breast cancer
• No uncontrolled infection
• No other co-morbidity that would interfere with patient's ability to participate in trial

PRIOR CONCURRENT THERAPY:

• No limit to prior therapy
• At least 4 weeks since prior melphalan or other myelosuppressive agents
• At least 2 weeks since prior non-myelosuppressive agents (e.g., thalidomide or high-dose corticosteroids)

• No concurrent high-dose corticosteroids

  • Concurrent chronic steroids (maximum dose 20 mg/day prednisone equivalent) allowed if they are being given for disorders other than amyloid (e.g., adrenal insufficiency or rheumatoid arthritis)
  • Concurrent continuation of low level/stable steroid doses for replacement or inhalation therapy allowed
• Concurrent bisphosphonates allowed
• No concurrent immunosuppressive medications such as cyclosporine
• No other concurrent investigational treatment
• No concurrent cytotoxic chemotherapy or external-beam radiotherapy
• No other concurrent systemic anti-neoplastic therapy including, but not limited to, immunotherapy, hormonal therapy, or monoclonal antibody therapy
• No concurrent prophylactic hematopoietic growth factors (unless for treatment of an established cytopenia)