Significance of Salvage Autologous Stem Cell Transplantation for Relapsed Multiple Myeloma: A Nationwide Retrospective Study in Japan.

Autologous stem cell transplantation (ASCT) has been employed for patients with relapsed multiple myeloma (MM) after up-front ASCT. The present retrospective study aimed to examine the survival benefit from salvage ASCT. Among 446 patients with relapsed MM after up-front single ASCT, 70 patients received salvage ASCT, the employment of which reduced the risk of mortality after relapse (p = 0.041). Using the parameters before initial ASCT, the advantage of salvage ASCT compared to standard therapy was confirmed in the subgroup with an international staging system stage of I or II (p = 0.040), good performance status (PS; p = 0.043), or no/mild renal comorbidity (p = 0.029). The advantage of salvage ASCT was also confirmed in the subgroup excluding those with early relapse within 7 months after initial ASCT (p = 0.026). Among patients who received salvage ASCT, a favorable prognosis is apparent for those with a time to relapse after initial ASCT of longer than 24 months. The overall survival after salvage ASCT was favorable excluding patients with the following factors: early relapse, poor PS, moderate/severe renal comorbidity, and progressive disease (p < 0.001). In conclusion, our results reinforced the evidence for encouraging salvage ASCT for eligible patients.