The purpose of this research study is to determine the safest dose of topotecan when given in a high dose before a stem cell transplant; topotecan will be given with melphalan.

The stem cells being transplanted are cells found in the bone marrow and blood that are responsible for making red blood cells, white blood cells, and platelets. The stem cells are collected by a process called leukapheresis and will be frozen for later use. After receiving the chemotherapy drugs, the stem cells will be thawed and given like a blood transfusion. This is called autologous stem cell transplant or rescue. The study doctors will be measuring how well the disease responds to the drugs as well as any side effects to the drugs. During the course of this study, blood and bone marrow samples will be obtained to measure levels of the chemotherapy drugs as well as levels of certain enzymes (proteins). The staff of the Blood and Marrow Transplant program will continue to collect information about the participant's disease and its treatment for the rest of their life.