Maintenance therapy after second autologous hematopoietic cell transplantation for multiple myeloma. A CIBMTR analysis.

The role of maintenance therapy after high-dose chemotherapy and first autologous transplantation in multiple myeloma (MM) is well established. We explored the effect of maintenance therapy on outcomes after salvage second autologous hematopoietic cell transplant (AHCT2) using the Center for International Blood and Marrow Transplant Research registry. Outcomes of interest included non-relapse mortality (NRM), relapse/progression (REL), progression-free and overall survival (PFS, OS). Of 522 patients who underwent AHCT2 between 2010 and 2018, 342 received maintenance therapy and 180 did not. Maintenance regimens included lenalidomide (42%), pomalidomide (13%), and bortezomib (13%). Median follow up was 58 months in the maintenance group and 61.5 months in the no-maintenance group. Univariate analysis showed superior outcomes at 5 years in maintenance compared to the no-maintenance group: NRM 2 (0.7-3.9)% vs 9.9 (5.9-14.9)%, (p < 0.01), REL 70.2 (64.4-75.8)% vs 80.3 (73.6-86.3)% (p < 0.01), PFS 27.8 (22.4-33.5)% vs. 9.8 (5.5-15.2)% (p < 0.01), and OS 54 (47.5-60.5)% vs 30.9 (23.2-39.2)% (p < 0.01), respectively. Use of maintenance therapy retained its association with improved outcomes in multivariate analysis. There was no difference in second cancers in the two groups (p = 0.39). We conclude that maintenance after AHCT2 is associated with improved 5-year outcomes.