The Role of Salvage Second Autologous Hematopoietic Cell Transplantation in Relapsed Multiple Myeloma.

Multiple myeloma (MM), a malignant disorder of plasma cells affecting primarily elderly patients, is the second most commonly diagnosed hematologic neoplasm. With the recent influx of effective new agents available, including proteasome inhibitors, immunomodulators, targeted monoclonal antibodies, and now chimeric antigen receptor T cell (CAR-T) therapy, the treatment landscape is evolving rapidly. Although the role of consolidative autologous stem cell transplantation (ASCT) in first remission is well established, in the relapsed setting after upfront ASCT, the role of a second ASCT (SAT) following reinduction is less clear and understudied. Practice patterns vary significantly across institutions, and most of the literature available to guide clinical decisions consists of single-institution experiences, with only 1 randomized study evaluating the role of SAT compared with a nontransplantation approach. SAT is likely underused, because it has not been included in clinical trials examining novel regimens for relapsed disease. Furthermore, outcomes likely can be improved with approaches to intensify the preparative regimen and the use of standard post-transplantation maintenance. In this review, we examine the role of SAT in the current MM treatment landscape in the context of recent data on the efficacy of CAR-T therapy in this disease. We caution the abandonment of SAT, given that CAR-T therapy is in its infancy in MM treatment, and that real-world data in the relapsed setting are consistently inferior to clinical trial outcomes.