Low-dose total-body irradiation and fludarabine followed by hematopoietic cell transplantation from HLA-identical sibling donors do not induce complete T-cell donor engraftment in most patients with progressive hematologic diseases

Objective The aim of this study was to determine whether nonmyeloablative transplants (NMT) result in complete and sustained donor engraftment in patients with progressive hematologic diseases compared to patients with stable disease or who are in remission. Materials and methods We prospectively monitored the kinetics of engrafting of T cells and myeloid cells in 10 consecutive adult patients with hematologic diseases submitted to NMT from an HLA-identical sibling donor. Patients were considered ineligible for conventional allogeneic transplantation because of age, concomitant diseases, or previous autologous transplant. Conditioning regimen and graft-vs-host disease posttransplant prophylaxis consisted of 2-Gy total-body irradiation plus fludarabine 30 mg/m2/day for 3 days, and cyclosporin and mycophenolate mofetil, respectively. Results One patient died in remission, and eight relapsed or progressed at a median of 68 days (15–335). On day +56, only 1 (11%) of 9 patients analyzed had achieved T-cell complete donor chimerism (CC), whereas 6 (67%) had achieved myeloid CC (p = 0.05). Median time for T-cell CC to occur was 110 days (56–150) compared with 42 days (28–100) to achieve myeloid CC (p = 0.002). The only parameter associated with T-cell CC was the status of the disease at the time of transplantation. Thus, 5 (100%) of 5 patients with stable disease or who were in remission before the transplant achieved T-cell CC compared with only 1 (20%) of 5 patients with progressive disease (p = 0.05). Conclusion Conditioning regimen based on fludarabine and 2-Gy total-body irradiation allows cell immunotherapy for old and medically infirm patients, but its antitumoral effect in patients with progressive hematologic disease is limited.