High-Dose Therapy and Autologous Hematopoietic Stem Cell Transplantation (ASCT) Has a Significant but Transient Impact on Quality of Life: Lessons From the Chronic Lymphocytic Leukemia (CLL) ASCT Study by the CLL Subcommittee of the Chronic Leukemia Working Party of the European Group for Blood and Marrow Transplantation