Long-Term Results of Prophylactic Donor Lymphocyte Infusions for Patients with Multiple Myeloma after Allogeneic Stem Cell Transplantation

The major reason for treatment failure after allografting in multiple myeloma (MM) is relapse. Donor lymphocyte infusions (DLIs) are considered a valuable post-transplant strategy mainly for relapsed patients but using them to prevent relapse in MM has been reported rarely. In the present study, we examined the efficacy of prophylactic DLIs after allogeneic hematopoietic stem cell transplantation (allo-HSCT) in myeloma patients with a long-term follow-up of more than 5 years. A total of 61 patients with MM who did not relapse or develop disease progression after allo-HSCT were treated with prophylactic DLI in an escalating fashion (overall 132 DLI procedures) to deepen remission status and prevent relapse. Overall response rate to DLI was 77%. Thirty-three patients (54%) upgraded their remission status, 41 patients (67%) achieved or maintained complete remission, and 26% achieved a molecular remission. Incidence of acute graft-versus-host disease (GVHD) grade II to IV was 33% and no DLI-related mortality was noted. After a median follow-up of 68.7 months from first DLI the estimated 8-year progression-free survival (PFS), and overall survival (OS) in a landmark analysis was 43% (95% confidence interval [CI], 28% to 57%) and 67% (95% CI, 53% to 82%), respectively, with best outcome for patients who acquired molecular remission (8-year PFS was 62% and 8-year OS was 83%). Prophylactic escalating DLI in a selected cohort of MM patients to prevent relapse after allograft resulted in a low incidence of severe GVHD and encouraging long-term results, especially if molecular remission is achieved.