Optimal timing of treatment at relapse after autologous stem cell transplantation in patients with multiple myeloma: a study of the Korean Multiple Myeloma Working Party (KMM-1909).

The effectiveness of early treatment for biochemical relapse of multiple myeloma (MM) is unclear. To clarify this issue, this retrospective study was performed to evaluate the survival outcomes of 315 patients with relapsed MM after upfront autologous stem cell transplantation (ASCT). Over a median follow-up of 66.6 months (range, 15.1-195.5 months), 48.2% of patients showed biochemical relapse, 41.3% showed clinical relapse, and 10.5% showed significant biochemical relapse. Progression-free survival (PFS) and overall survival (OS) were inferior for patients with clinical relapse compared to the other patients. Multivariate analysis showed that clinical relapse was an independent prognostic factor for OS. In patients with biochemical relapse, there was no significant difference in survival between patients treated while asymptomatic and those treated once clinical symptoms had appeared. Relapse type after upfront ASCT was a significant prognostic factor in patients with MM. In addition, no survival benefit of early treatment at biochemical relapse was observed, but a triplet regimen may be beneficial for MM patients with biochemical relapse.