Melphalan With or Without Holmium Ho 166 DOTMP Followed by Peripheral Stem Cell Transplantation in Treating Patients With Multiple Myeloma

RATIONALE: Drugs used in chemotherapy use different ways to stop tumor cells from dividing so they stop growing or die. Radioactive drugs such as holmium Ho 166 DOTMP can kill cancer cells without harming healthy cells. Peripheral stem cell transplantation may be able to replace immune cells that were destroyed by chemotherapy or radiation therapy used to kill tumor cells. PURPOSE: Randomized phase III trial to compare the effectiveness of melphalan with or without holmium Ho 166 DOTMP followed by peripheral stem cell transplantation in treating patients who have multiple myeloma.