Characteristics of exceptional responders to autologous stem cell transplantation in multiple myeloma

Autologous stem cell transplantation (ASCT) is an important treatment modality in multiple myeloma (MM). However, relapse following ASCT is considered almost inevitable. This study aimed to characterize exceptional responders to ASCT, defined as progression-free survival (PFS) >8 years in the absence of maintenance therapy. We retrospectively analyzed patients treated at Mayo Clinic between August 1, 1998 and January 3, 2006, and included those with symptomatic MM, treated with an ASCT within 12 months of diagnosis. We found that 46 (9%) of the 509 patients who underwent ASCT during the study period were exceptional responders. The median duration of follow-up from diagnosis was 16.2 (interquartile range 14.3–17.7) years. The best response to therapy was a complete response (CR) or better in 34 (74%) of patients, and less than a CR in 12 (26%) of patients. The median PFS was 13.8 (95% confidence interval 10.5–18.5) years, and at the time of the last hematology assessment, 24 of 46 (52%) patients remained in remission. In conclusion, we showed that a small subset of patients with MM attains durable disease control without maintenance therapy post ASCT. Pre-emptive identification of these patients may help prevent undue toxicities and costs of subsequent therapy.