This project will evaluate the efficacy and safety of the conditioning regimen bortezomib-bendamustine-melphalan (BBM) in combination with autologous hematopoietic stem cell transplantation (ASCT) in relapsed multiple myeloma given from 2011 to 2018 at Uppsala University Hospital. This approach will be retrospectively compared to high dose melphalan (HDM) in the same setting in the years prior to, and following the BBM-period. Data on efficacy and safety data will be collected through systematic analysis of electronic medical records and from the Swedish Cancer Registry.