Early M‐protein immune reconstitution after autologous haematopoietic stem cell transplantation is a good prognostic marker for patients with high‐risk cytogenetic multiple myeloma

Summary The presence of transient abnormal protein banding (M‐protein immune reconstitution) in serum immunofixation electrophoresis after autologous haematopoietic stem cell transplantation in patients with multiple myeloma has been reported. The purpose of this study was to investigate the impact of post‐transplant M‐protein immune reconstitution on the prognosis of patients with multiple myeloma. M‐protein immune reconstitution was observed in 25.9% (75/290) of patients. The CR rate and MRD negativity were higher in the M‐protein immune reconstitution group (85.3% vs. 69.3%, p = 0.013, 81.9% vs. 66.5%, p = 0.014). Although there were no significant differences between the groups, the overall median survival time was longer in the M‐protein immune reconstruction group (80 vs. 72 m, p = 0.076; not reached vs. 105 m, p = 0.312). Among patients in the cytogenetic high‐risk group, the occurrence of M‐protein immune reconstitution predicted better PFS and OS (80 vs. 31 m, p = 0.010; not reached vs. 91 m, p = 0.026). Additionally, in revised‐International Staging System stage III patients, PFS and OS were better in those who achieved M‐protein immune reconstitution (80 vs. 20 m, p = 0.025; 57 vs. 32 m, p = 0.103). The better prognosis of M‐protein immune reconstitution patients may be associated with the acquisition of a deeper response. In high‐risk patients, early acquisition of M‐protein immune reconstitution may suggest a better prognosis.