Significance of salvage autologous stem cell transplantation (ASCT) for patients with multiple myeloma relapsing after up-front ASCT

We retrospectively analyzed data from 60 patients who had relapsed after up-front autologous stem cell transplantation (ASCT). Thirteen patients received salvage ASCT, and median progression-free survival (PFS) and overall survival (OS) after salvage ASCT were 19.3 and 41.1 months, respectively. Favorable factors for PFS after salvage ASCT were as follows; achieving a partial or better response before salvage ASCT [hazard ratio (HR) =0.018, 95% confidence interval (CI): 0.005-0.64, P=0.028] and consolidation/maintenance therapy after salvage ASCT (HR=0.083, 95% CI: 0.008-0.87, P=0.038). There was no significant factor for OS after salvage ASCT. Patients without salvage ASCT had not been surveyed for PFS after relapse. Including all patients, two unfavorable factors for OS after relapse were as follows; relapsing during or after consolidation/maintenance therapy after initial ASCT and salvage therapy comprising cytotoxic agents. On the other hand, salvage ASCT was favorable for OS after relapse post initial ASCT (HR=0.30, 95% CI: 0.096-0.95, P=0.041). Confounding factors and survivor treatment selection bias do not permit definitive conclusion. We hope the current study sheds light on the salvage ASCT, but careful evaluation is needed during the approval of additional new agents.