Dose intensity and the toxicity and efficacy of allogeneic hematopoietic cell transplantation

Irradiation and bone marrow reconstitution affect the functional Ly49 natural killer cell repertoire in rats

Total body irradiation (TBI) is part of the preconditioning regimen for allogeneic bone marrow transplantation (alloBMT) and the procedure is associated with treatment-related toxicity and delayed immune reconstitution. Natural killer (NK) cells develop and acquire functional competence in close interaction with stromal bone marrow cells that are considered relatively radioresistant compared to the hematopoietic compartment. We thus undertook a study to assess the effect of TBI on the reconstitution of class I MHC-specific Ly49 NK cell receptors in a rat model of alloBMT. In rats subjected to TBI alone or followed by MHC-matched BMT, the irradiation conditioning induced a skewing of the Ly49 repertoire. Specifically, the activating Ly49s3^bright subset exhibited increased frequency and receptor density which correlated with augmented alloreactivity relative to untreated control rats. Our results highlight the plasticity of NK cells and indicate that ionizing radiation (IR) affects the stromal compartment and as a consequence the maturation and functional properties of bone marrow-derived NK cells. These changes lasted throughout the 6 months observation period, showing that irradiation induces long term effects on the generation of the NK cell receptor repertoire.

Alternative donor transplantation for older patients with acute myeloid leukemia in first complete remission: a center for international blood and marrow transplant research-eurocord analysis

We studied patients with acute myeloid leukemia (AML) over age 50 and in first complete remission (CR1) after adult unrelated donor (URD) (n = 441, 8/8 HLA matched; n = 94, 7/8 HLA matched) or umbilical cord blood (UCB; n = 205) transplantations. UCB recipients achieved CR1 within 8 weeks less often, and received reduced-intensity conditioning and cyclosporine-based graft-versus-host disease (GVHD) prophylaxis more often. Neutrophil recovery was slower in UCB (69% by day 28) compared with 8/8 HLA-matched URD (97%) and 7/8 HLA-matched (91%) (P < .001) recipients. Three-year transplantation-related mortality (TRM) was higher and leukemia-free survival (LFS) lower with UCB (35% and 28%, respectively) versus 8/8 HLA-matched URD (27% and 39%, respectively). TRM was higher in 7/8 HLA-matched URD (41%, P = .01), but LFS was similar at 34% (P = .39). Three-year chronic GVHD was the lowest in UCB (28%) versus 53% and 59% in 8/8 and 7/8 HLA-matched URD recipients, respectively. Three-year survival was 43% in 8/8 HLA-matched URD (95% confidence interval [CI], 38% to 48%), 30% in UCB (95% CI, 23% to 37%) (P = .002) and 37% in 7/8 URD (95% CI, 27 to 46). Allotransplantation for AML in CR1 with any of these grafts extends LFS for over one third of older patients. In the absence of an 8/8 HLA-matched URD or when transplantation is needed urgently, UCB can provide extended survival. Less frequent chronic GVHD with UCB transplantation may be of particular value for older patients.

Chimerism and outcomes after allogeneic hematopoietic cell transplantation following nonmyeloablative conditioning

Allogeneic hematopoietic cell transplantation (HCT) following nonmyeloablative conditioning has been extensively evaluated in patients with hematologic malignancies who are ineligible for conventional HCT because of age or medical comorbidities. Nonmyeloablative regimens have led to an initial state of mixed hematopoietic chimerism defined as coexistence of donor- and host-derived hematopoiesis. While nonmyeloablative regimens have been associated with reduced regimen-related toxicities in comparison with conventional myeloablative conditioning, graft rejection, graft-versus-host disease (GVHD), and disease progression have remained significant challenges. In this article, after briefly introducing current techniques for chimerism assessment, we describe factors affecting donor chimerism levels after nonmyeloablative conditioning, and then review data suggesting that chimerism assessment early after HCT might help identify patients at risk for graft rejection, GVHD and relapse/progression. Finally, we discuss how these observations have opened the way to further research protocols evaluating manipulation of postgrafting immunosuppression, and/or infusion of donor immune cells.

High doses of transplanted CD34+ cells are associated with rapid T-cell engraftment and lessened risk of graft rejection, but not more graft-versus-host disease after nonmyeloablative conditioning and unrelated hematopoietic cell transplantation

This report examines the impact of graft composition on outcomes in 130 patients with hematological malignancies given unrelated donor granulocyte-colony-stimulating-factor-mobilized peripheral blood mononuclear cells (G-PBMC) (n = 116) or marrow (n = 14) transplantation after nonmyeloablative conditioning with 90 mg/m(2) fludarabine and 2 Gy TBI. The median number of CD34(+) cells transplanted was 6.5 x 10(6)/kg. Higher numbers of grafted CD14(+) (P = 0.0008), CD3(+) (P = 0.0007), CD4(+) (P = 0.001), CD8(+) (P = 0.004), CD3(-)CD56(+) (P = 0.003), and CD34(+) (P = 0.0001) cells were associated with higher levels of day 28 donor T-cell chimerism. Higher numbers of CD14(+) (P = 0.01) and CD34(+) (P = 0.0003) cells were associated with rapid achievement of complete donor T-cell chimerism, while high numbers of CD8(+) (P = 0.005) and CD34(+) (P = 0.01) cells were associated with low probabilities of graft rejection. When analyses were restricted to G-PBMC recipients, higher numbers of grafted CD34(+) cells were associated with higher levels of day 28 donor T-cell chimerism (P = 0.01), rapid achievement of complete donor T-cell chimerism (P = 0.02), and a trend for lower risk for graft rejection (P = 0.14). There were no associations between any cell subsets and acute or chronic GVHD nor relapse/progression. These data suggest more rapid engraftment of donor T cells and reduced rejection rates could be achieved by increasing the doses of CD34(+) cells in unrelated grafts administered after nonmyeloablative conditioning.

Role of Allogeneic Stem Cell Transplantation in Current Treatment of Acute Myeloid Leukemia

Allogeneic hematopoietic stem cell transplantation (alloSCT) has been established as an effective consolidation therapy in acute myeloid leukemia (AML) in first or subsequent remission. Although it effectively prevents relapse, treatment-related mortality (TRM) associated with alloSCT may compromise that beneficial effect. As a result, alloSCT may be restricted to patients with a relatively high risk of relapse. Here, we review studies that identify categories of AML patients who may specifically benefit from alloSCT. In addition, we discuss recent developments with respect to alternative donors, stem cell sources, and supportive care. Finally, we highlight recent results obtained with reduced-intensity alloSCT, which already significantly influence our therapeutic strategy in elderly patients with AML.