DISEASE CHARACTERISTICS: Histologically confirmed multiple myeloma Newly diagnosed, drug sensitive (i.e., greater than 50% response to standard chemotherapy), and poor prognostic indicators (e.g., Salmon-Durie stage III, serum beta-2-microglobulin greater than 3.0 ug/L, high proliferative fraction, or hypodiploidy) OR Relapsed after a response to standard chemotherapy OR Primary refractory disease No active leptomeningeal involvement History of prior CSF tumor involvement without symptoms or signs allowed provided CSF is now free of disease on lumbar puncture and MRI of brain shows no tumor involvement No severe symptomatic CNS disease of any etiology