RATIONALE: Drugs used in chemotherapy use different ways to stop cancer cells from dividing so they stop growing or die. Peripheral stem cell transplantation may allow the doctor to give higher doses of chemotherapy drugs and kill more cancer cells. Colony-stimulating factors such as filgrastim and sargramostim may increase the number of immune cells found in bone marrow or peripheral blood and may help a person's immune system recover from the side effects of chemotherapy. Interferon alfa may interfere with the growth of cancer cells. It is not yet known which treatment regimen is more effective for multiple myeloma.