Inclusion Criteria

DISEASE CHARACTERISTICS: Newly diagnosed multiple myeloma (diagnosis within 12 months of
study) and scheduled to undergo autologous peripheral blood stem cell transplantation
Prior diagnosis of monoclonal gammopathy of undetermined significance (MGUS) or smoldering
myeloma (SMM) allowed if the criteria for diagnosis of multiple myeloma was met within 12
months of study Serum or urinary M-protein confirmation of diagnosis (IgA, IgD, IgG, IgE,
or light chain proteins) At least 10% plasma cells in bone marrow Must have received
induction therapy without disease progression or relapse after initial response Prior
induction therapy must have been completed no more than 6 months before stem cell
collection and no more than 9 months before transplantation Must have undergone stem cell
mobilization with cyclophosphamide IV and filgrastim (G-CSF) The following diagnoses are
excluded: Non-secretory multiple myeloma IgM myeloma Solitary bone or extramedullary
plasmacytoma Symptomatic MGUS or SMM Symptomatic indolent multiple myeloma

PATIENT CHARACTERISTICS: Age: 18 to 70 Performance status: ECOG 0-2 Life expectancy: Not
specified Hematopoietic: See Disease Characteristics Hepatic: Bilirubin no greater than 2
mg/dL SGPT no greater than 2 times upper limit of normal No clinical evidence of
amyloidosis involving the liver Renal: Creatinine no greater than 2.0 mg/dL Creatinine
clearance at least 30 mL/min No clinical evidence of amyloidosis involving the kidney
Cardiovascular: LVEF at least 50% No evidence of amyloidosis on echocardiogram No
uncontrolled arrhythmia No symptomatic cardiac disease Pulmonary: FEV1 at least 60% OR FVC
at least 60% OR DLCO at least 60% No symptomatic pulmonary disease No clinical evidence of
amyloidosis involving the lungs Other: HIV negative No cord compression No other
concurrent illness that would preclude survival No clinical evidence of amyloidosis
involving the autonomic nervous system or gastrointestinal tract No known allergy to
vitamin C Not pregnant or nursing Negative pregnancy test Fertile patients must use
effective contraception

PRIOR CONCURRENT THERAPY: Biologic therapy: See Disease Characteristics No prior
thalidomide for myeloma No prior peripheral blood stem cell or bone marrow transplantation
No concurrent thalidomide No concurrent interferon Chemotherapy: See Disease
Characteristics No prior clarithromycin for myeloma No more than 2 courses of prior
induction therapy containing an alkylating agent Endocrine therapy: No concurrent
dexamethasone Radiotherapy: No prior radiotherapy to more than 20% of bone marrow No
greater than 30 Gy to the spinal cord Surgery: Not specified Other: At least 28 days since
prior bisphosphonates No prior new or experimental agents for myeloma No concurrent
experimental therapies No concurrent bisphosphonates