Objective: To explore the regimen-related toxicity (RRT) and therapeutic effects of very-high-dose conditioning regimen combined with induction of graft-versus-leukemia (GVL) effects in allogeneic hematopoietic stem cell transplantation (allo-HSCT) for refractory leukemia with unattainable complete remission (CR) before transplantation.
Methods: Eighteen patients who failed to obtain CR before transplantation received very-high-dose conditioning regimen protocol (experimental group), and 62 patients with acute leukemia with CR or with chronic myeloid leukemia in the chronic phase before transplantation received total body irradiation plus cyclophosphamide (CTX) or modified BuCY (hydroxyurea, busulfan, Ara-C, CTX) protocol (control group). In patients with refractory leukemia who did not develop graft-versus-host disease (GVHD) 30 d after the transplantation, GVL was induced by rapid reduction of the dosage of cyclosporin A or by donor lymphocytic infusion. The incidence and mortality of RRT and the rates of CR, GVHD and leukemia relapse after transplantation were investigated. Kaplan-Meier survival analysis model was used to estimate the disease-free survival (DFS) rate at 3 years post-transplantation.
Results: Except for one patient in the experimental group and two in the control group who died of transplantation- related complications, all the other patients obtained hematopoietic reconstitution. The total incidence of RRT was 100% in both groups, involving most frequently the stomach and intestines at the rate as high as 83.3% in the experimental group and 85.5% in the control group. RRT involving the oral cavity occurred in 44.4% and 62.9%, and that involving the bladder in 16.7% and 33.9% of the cases in the experimental group and control group, respectively, all similar between the groups (P=0.823, 0.172 and 0.244, respectively). The RRT mortality was 0 and 5% in the experimental and control groups, respectively (P=0.341). With the exception of one patient who died of infection, all the other patients treated with very-high-dose conditioning regimen obtained CR. The incidences of acute/chronic GVHD were 58.8%/92.6% and 40.0%/55.8%, respectively, in the experimental and control groups. The incidence of leukemia relapse was 11.8% and 18.3%, and DFS at 3 years after transplantation was (61.2+/-12.3)% and (65.0+/-7.4)% (P=0.6311) in the two groups, respectively.
Conclusion: Consecutive very-high-dose conditioning regimen combined with GVL induction after transplantation can increase the rate of CR and DFS, without increasing RRT incidence and mortality in allo-HSCT for the refractory leukemia with unattainable CR pre-transplantation.