RATIONALE: Thalidomide may stop the growth of multiple myeloma by stopping blood flow to the tumor. Prednisone may be effective in preventing relapse of multiple myeloma.

PURPOSE: Randomized phase II trial to compare the effectiveness of two doses of thalidomide combined with prednisone following peripheral stem cell transplantation in treating patients who have multiple myeloma.

OBJECTIVES: I. Determine which dose of thalidomide (200 mg vs 400 mg) combined with prednisone is the optimally tolerated dose when used as maintenance therapy following autologous stem cell transplantation in patients with multiple myeloma. II. Compare the response rate in patients treated with these regimens. III. Compare the progression-free and overall survival in patients treated with these regimens.

OUTLINE: This is a randomized, open-label, multicenter study. Patients are stratified according to age (60 and over vs under 60). Within 60-100 days after autologous stem cell transplantation, patients are randomized to 1 of 2 treatment arms. Arm I: Patients receive lower dose oral thalidomide daily and oral prednisone every other day. Arm II: Patients receive higher dose thalidomide daily and oral prednisone every other day. Treatment continues for 2 years in the absence of disease progression or unacceptable toxicity. Patients are followed monthly for 6 months, every 3 months, and then at time of disease progression.

PROJECTED ACCRUAL: A total of 40-80 patients (20-40 per arm) will be accrued for this study within 17-21 months.

DISEASE CHARACTERISTICS: Histologically proven multiple myeloma Initial diagnosis must have been confirmed by one of the following prior to initial treatment for multiple myeloma: Biopsy of an osteolytic lesion or soft tissue tumor composed of plasma cells Bone marrow aspirate and/or biopsy demonstrating at least 10% plasmacytosis Bone marrow containing less than 10% plasma cells but with at least 1 bony lesion and the M-protein criteria outlined below Measurable serum M-component of IgG, IgA, IgD, or IgE at initial diagnosis OR If only light chain disease (urine M-protein only) present, then the urinary excretion of light chain (Bence Jones) protein must have been at least 1.0 g/24 hours at time of initial diagnosis Must have undergone autologous stem cell transplantation within 1 year of beginning initial chemotherapy for multiple myeloma Must be randomized 60-100 days after autologous stem cell infusion No evidence of progressive disease

PATIENT CHARACTERISTICS: Age: 16 and over Performance status: ECOG 0-2 Life expectancy: At least 6 months Hematopoietic: See Disease Characteristics Granulocyte count at least 1,000/mm3 Platelet count at least 100,000/mm3 Hepatic: AST and/or ALT no greater than 1.5 times upper limit of normal (ULN) Alkaline phosphatase no greater than 1.5 times ULN Renal: Creatinine no greater than 3 times ULN Cardiovascular: No uncontrolled hypertension Other: Not pregnant or nursing Negative pregnancy test Fertile female patients must use 2 effective methods of contraception (1 barrier and 1 hormonal) during and for 1 month after study Fertile male patients must use effective barrier contraception during and for 1 month after study No other medical condition that would preclude long term use of prednisone or thalidomide No other malignancy within the past 5 years except adequately treated squamous cell or basal cell skin cancer or carcinoma in situ of the cervix No diabetes with end stage organ damage No history of gastric ulceration or bleeding No avascular necrosis of the hips No peripheral neuropathy causing symptomatic dysfunction Sensory symptoms induced by vincristine allowed No demonstrated hypersensitivity to thalidomide or its components No other major medical illness that would increase risk or preclude study No employment that prohibits the use of sedatives (due to known effect of thalidomide)

PRIOR CONCURRENT THERAPY: Biologic: See Disease Characteristics No prior thalidomide Chemotherapy: See Disease Characteristics Endocrine: Not specified Radiotherapy: Not specified Surgery: Not specified Other: No other concurrent anticancer treatment No other concurrent investigational therapy