Inclusion Criteria

DISEASE CHARACTERISTICS:

- At least 1 of the following diagnoses:

- Multiple myeloma

- Stage II or III disease

- At least 1 of the following must be present:

- Serum M-protein of IgG, IgA, IgD, IgE greater than 1.0 g/dL

- Urinary M-protein (Bence-Jones) at least 200 mg/24 hours

- No IgM peaks except in patients who have physiologic criteria to support a
diagnosis of multiple myeloma (e.g., bony lesions, myeloma kidney-cast
nephropathy, absence of adenopathy [unless pathology-proven to be plasma
cell infiltration])

- No monoclonal gammopathy of undetermined significance

- No indolent or smoldering myeloma

- No disease progression on prior thalidomide or dexamethasone

- Histologically confirmed primary systemic amyloidosis

- No senile, secondary, localized, dialysis-related, or familial amyloidosis

- No severe cardiac involvement

- No pre-exertional syncope, ventricular arrhythmia, or symptomatic
pleural effusions associated with cardiac involvement

- Light Chain Deposition Disease alone or in combination with multiple myeloma
meeting the following criteria:

- Deposition of granular material containing free light
chains/immunoglobulins that did not bind Congo red

- Evidence of plasma cell dyscrasia (i.e., monoclonal gammopathy in the serum
or urine by immunofixation electrophoresis and/or clonal plasmacytosis) on
bone marrow biopsy by immunohistochemistry and/or elevated serum-free light
chain concentration

- Must have been diagnosed within the past year

- Concurrent enrollment in the myeloma repository protocol SWOG-S0309 must be offered

PATIENT CHARACTERISTICS:

Age

- 18 and over (patients with amyloidosis only OR patients with amyloidosis and multiple
myeloma OR patients with multiple myeloma only with poor renal function) OR

- 70 and over (patients with multiple myeloma only with or without poor renal function)

Performance status

- Zubrod 0-2

Life expectancy

- Not specified

Hematopoietic

- Absolute neutrophil count at least 1,000/mm^3

- Platelet count at least 100,000/mm^3

Hepatic

- Bilirubin no greater than 2.5 times upper limit of normal (ULN)

- SGOT or SGPT no greater than 2.5 times ULN

Renal

- No hemodialysis within 2 hours of melphalan or stem cell infusion

Cardiovascular

- See Disease Characteristics

- Hemodynamically stable (i.e., systolic blood pressure > 90 mm Hg in a lying position
within the past 42 days)

- No myocardial infarction within the past 6 months

- No congestive heart failure

- No arrhythmia refractory to medical therapy

- LVEF greater than 45% by echocardiogram or MUGA

Pulmonary

- See Disease Characteristics

- No history of chronic obstructive or chronic restrictive pulmonary disease

- Pulmonary function studies (e.g., FEV_1 and FVC) at least 50% of predicted

- DLCO at least 50% of predicted

- Normal high resolution CT scan of the chest and acceptable arterial blood gases
(i.e., PO_2 greater than 70) required for patients unable to complete pulmonary
function tests due to bone pain or fracture

Other

- Not pregnant or nursing

- Negative pregnancy test

- Fertile patients must use effective contraception

- Multiple myeloma patients receiving thalidomide must use 2 methods of effective
contraception for at least 4 weeks before, during, and for at least 4 weeks
after discontinuation of thalidomide

- HIV negative

- No other concurrent significant medical condition

- No concurrent uncontrolled life-threatening infection

- No other malignancy within the past 5 years except adequately treated basal cell or
squamous cell skin cancer, carcinoma in situ of the cervix, or adequately treated
stage I or II cancer currently in complete remission

PRIOR CONCURRENT THERAPY:

Biologic therapy

- See Disease Characteristics

Chemotherapy

- See Disease Characteristics

- Prior cumulative melphalan dose no more than 200 mg

- No other concurrent chemotherapy

Endocrine therapy

- See Disease Characteristics

- No concurrent hormonal therapy

Radiotherapy

- No concurrent radiotherapy

Surgery

- Not specified

Other

- Recovered from prior therapy

- Prior or concurrent bisphosphonates allowed