Low-Dose Total Body Irradiation (TBI) Followed by Donor Lymphocyte Infusion Increases Donor T-Cell Chimerism Levels in Patients with Low Donor T-Cell Chimerism after Nonmyeloablative Conditioning.

Background. Low donor T-cell chimerism levels after allogeneic hematopoietic cell transplantation (HCT) with nonmyeloablative conditioning have been associated with high risks of both graft rejection and relapse/progression (

Methods. Conditioning regimen for HCT consisted of 2 Gy TBI with (n=15) or without (n=11) added fludarabine. 20 patients received PBSC from related, and 6 PBSC from HLA-matched unrelated donors. Peripheral blood stem cells (PBSC) were unmanipulated in 15 patients, and CD8-depleted in the 11 remaining patients. Indication for TBI/DLI included < 50% donor T-cell chimerism or decrement of donor T-cell chimerism by 20% (or 10% if below 60%). Depending of patient-donor relationship, DLIs were given at a dose of 1 to 10 × 107 T-cells/kg (median 2 × 107 T-cells/kg), 42 to 725 days (median 68.5 days) following HCT. Prophylactic postgrafting immunosuppression was pursued after DLI in all but one patients.

Results. Before DLI, donor T-cell chimerism levels ranged from 15 to 77% (median 44%) in the DLI group, versus from 24 to 66% (median 47%) in the TBI/DLI group (P=0.66). Two months after DLI, donor T-cell chimerism levels ranged from 15 to 93% (median 53%) in the DLI group (P=0.10 in comparison to before DLI), versus from 20 to 98% (median 56%) in the TBI/DLI group (P=0.04 in comparison to before DLI) (Figure 1). In addition, 0 of 15 patients in the DLI group versus 5 of 15 patients in the TBI/DLI group had > 25% increased T-cell chimerism levels 2 months after DLI (P=0.04). Highest T-cell chimerism levels after DLI ranged from 15 to 99% (median 71%) in the DLI group, versus from 43 to 100% (median 96%) in the TBI/DLI group (P=0.06). Further, 2 of 15 patients in the DLI group, versus 0 of 15 patients in the TBI/DLI group experienced graft rejection. In the DLI group, 3 patients developed grade II–IV acute GVHD (2 grade II and 1 grade IV), while 1 patient in the TBI/DLI group experienced grade II acute GVHD. TBI/DLI was followed by grade IV hematologic toxicities in most patients, but most of them remained treated in the outpatient clinic. One-year overall survival was 67% in the DLI group versus 73% in the TBI/DLI group (NS).

Conclusions. DLI increased donor T-cell chimerism levels in a number of patients when preceeded by low dose TBI. However, hematological toxicity of TBI/DLI was relatively high, with most patients requiring several RBC and Plt transfusions. Further studies are needed to assess its impact on HCT outcomes.

View largeDownload slide

Figure

View largeDownload slide

Figure

Close modal