Reduced-intensity transplantation with in vivo T-cell depletion and adjuvant dose-escalating donor lymphocyte infusions for chemotherapy-sensitive myeloma: limited efficacy of graft-versus-tumor activity.

Reduced-intensity conditioning regimens allow application of allogeneic stem cell transplantation to greater numbers of patients with myeloma by reducing transplantation-related mortality. We prospectively evaluated the role of an approach incorporating in vivo T-cell depletion and subsequent adjuvant donor lymphocyte infusions (DLIs) as part of front-line therapy for chemotherapy-sensitive multiple myeloma. Twenty patients with HLA-matched related (n = 12) or unrelated (n = 8) donors entered the study. None had previously undergone autologous transplantation. Acute graft-versus-host disease (GVHD) following transplantation was minimal (3 grade II and no grade III or IV). Nonrelapse mortality rate was relatively low (15%) compared with conventional myeloablative allogeneic transplantation series, although it remained significantly higher than in the autologous setting. Disease responses by 6 months posttransplantation were modest (2 in complete remission, 4 in partial remission, 2 were minimally responsive, 6 had no change, 3 had progressive disease, and 3 were not evaluable). Fourteen patients received escalating-dose DLI for residual/progressive disease. Three developed acute GVHD and 2 developed limited chronic GVHD. Seven demonstrated further disease responses, which appeared to be more common in those developing GVHD (5 of 5 versus 2 of 9; P =.02). All responses were associated with conversion from mixed to full donor T-cell chimerism. Response durations were disappointing (5 <12 months) and progression often occurred despite persisting full donor chimerism. Two-year estimated overall survival and current progression-free survival rates (intention to treat with DLI from 6 months) were 71% and 30%, respectively. The current approach incorporating T-cell depletion appears excessively immunosuppressive despite attempts to restore immune function with DLI. Dose escalation failed to allow convincing dissociation of graft-versus-myeloma from GVHD. Attempts to hasten immune reconstitution and to focus and amplify appropriate components of allogeneic T-cell responses will be required to increase complete remission rates and response durations.