Stem Cell Harvesting after Bortezomib-Based Reinduction for Myeloma Relapsing after Autologous Transplantation: Results from the British Society of Blood and Marrow Transplantation/United Kingdom Myeloma Forum Myeloma X (Intensive) Trial

The phase III British Society of Blood and Marrow Transplantation/United Kingdom Myeloma Forum Myeloma X trial (MMX) demonstrated prospectively, for the first time, superiority of salvage autologous stem cell transplantation over chemotherapy maintenance for multiple myeloma (MM) in first relapse after previous ASCT. However, many patients have stored insufficient stem cells (PBSC) for second ASCT and robust evidence for remobilization after first ASCT is lacking. We report the feasibility, safety, and efficacy of remobilization after bortezomib-doxorubicin-dexamethasone reinduction in MMX and outcomes of second ASCT with these cells. One hundred ten patients underwent ≥1 remobilization with 32 and 4, undergoing second and third attempts, respectively. Toxicities of remobilization were similar to those seen in first-line mobilization. After all attempts, 52% of those with insufficient previously stored PBSC had harvested a sufficient quantity to proceed to second ASCT. Median PBSC doses infused, neutrophil engraftment, and time to discharge after second ASCT were similar regardless of stem cell source, as were the toxicities of second ASCT. No significant differences between PBSC sources were noted in depth of response to ASCT or time to progression. Harvesting after bortezomib-doxorubicin-dexamethasone reinduction for MM at first relapse is safe and feasible and yields a reliable cell product for second ASCT. The study is registered with ClinicalTrials.gov (NCT00747877) and EudraCT (2006-005890-24).