Increasing T-cell age reduces effector activity but preserves proliferative capacity in a murine allogeneic major histocompatibility complex-mismatched bone marrow transplant model

Allogeneic Hematopoietic Cell Transplantation for Older Adults with Acute Myeloid Leukemia

Acute myeloid leukemia (AML) is a disease that affects adults aged 65 years and above, and survival in this population is poor. Allogeneic hematopoietic cell transplantation (allo-HCT) is a potentially curative therapy for these patients but is underutilized due to frequent comorbidities and perceived higher risk of treatment-related mortality and non-relapse mortality. Increasing data supports the utility of allo-HCT in fit older patients after intensive chemotherapy resulting in improvement of outcomes. With the development of reduced intensity and non-myeloablative conditioning regimens that are associated with lower rates of treatment-related toxicity and mortality, this has allowed more older patients with AML to receive allo-HCT. In this review, we provide some guidance on appropriate selection of older patients as transplant candidates, benefits and risks associated with allo-HCT, conditioning regimen choice, and stem cell transplant sources as they relate to the conduct of stem cell transplantation in older patients.

In patients older than 55 years with AML in first CR, should we search for a matched unrelated donor when an old sibling donor is available?

Allogeneic hematopoietic transplantation is increasingly used in patients aged 55 years or more with AML. The question of whether outcomes can be improved with an allele-level 8/8 HLA-matched unrelated donor (MUD) rather than an older HLA-matched sibling (MSD, more than 55 years) is still unanswered. We thus analyzed outcomes in 714 patients aged 55 years and older with AML in first CR (CR1) who received PBSCs after a reduced-intensity conditioning hematopoietic cell transplant from a MUD (n=310) or a MSD (n=404) in a recent period (2005-2010). The 3-year cumulative incidences (CIs) of non-relapse mortality were 17% and 23% with MSD and MUD, respectively (P=0.17). The 3-year CIs of relapse were 37% and 30%, respectively (P=0.12), resulting in a 3-year CI of leukemia-free survival of 46% and 47%, respectively (P=0.51). The 3-year overall survival was 49% with both MSD and MUD. In conclusion, HLA-identical sibling donors aged 55 years or more should not be excluded because of age for patients aged 55 years and older with AML in CR1.

Pre-transplant prognostic factors of long-term survival after allogeneic peripheral blood stem cell transplantation with matched related/unrelated donors

Mobilized peripheral blood has become the predominant stem cell source for allogeneic hematopoietic cell transplantation. In this retrospective single center study of 442 patients with hematologic malignancies, we analyzed prognostic factors for long-term survival after peripheral blood stem cell transplantation from HLA-matched related or unrelated donors. To account for disease/status heterogeneity, patients were risk-stratified according to the Disease Risk Index. Five-year overall survival was similar after transplants with matched related and unrelated donors (45% and 46%, respectively; P=0.49). Because donor age ≥60 years impacted outcome during model building, we further considered 3 groups of donors: matched unrelated (aged <60 years by definition), matched related aged <60 years and matched related aged ≥60 years. In multivariate analysis, the donor type/age group and the graft CD34(+) and CD3(+) cell doses impacted long-term survival. Compared with matched unrelated donor transplant, transplant from matched related donor <60 years resulted in similar long-term survival (P=0.67) while transplant from matched related donor ≥60 years was associated with higher risks for late mortality (hazard ratio (HR) 4.41; P=0.006) and treatment failure (HR: 6.33; P=0.009). Lower mortality risks were observed after transplant with CD34(+) cell dose more than 4.5×10(6)/kg (HR: 0.56; P=0.002) and CD3(+) cell dose more than 3×10(8)/kg (HR: 0.61; P=0.01). The Disease Risk Index failed to predict survival. We built an "adapted Disease Risk Index" by modifying risks for myeloproliferative neoplasms and multiple myeloma that improved stratification ability for progression-free survival (P=0.04) but not for overall survival (P=0.82).

Who is the better donor for older hematopoietic transplant recipients: an older-aged sibling or a young, matched unrelated volunteer?

Older patients are increasingly undergoing allogeneic hematopoietic transplantation. A relevant question is whether outcomes can be improved with a younger allele-level 8/8 HLA-matched unrelated donor (MUD) rather than an older HLA-matched sibling (MSD). Accordingly, transplants in leukemia/lymphoma patients age ≥50 years were analyzed comparing outcomes for recipients of MSD ≥50 (n = 1415) versus MUD <50 years (n = 757). Risks of acute graft-versus-host disease (GVHD) grade 2 to 4 (hazard ratio [HR], 1.63; P < .001), 3 to 4 (HR, 1.85; P < .001), and chronic GVHD (HR, 1.48; P < .0001) were higher after MUD compared with MSD transplants. The effect of donor type on nonrelapse mortality (NRM), relapse, and overall mortality was associated with performance score. For patients with scores of 90 or 100, NRM (HR, 1.42; P = .001), relapse (HR, 1.45; P < .001), and overall mortality (HR, 1.28; P = .001) risks were higher after MUD transplants. For patients with scores below 90, NRM (HR, 0.96; P = .76), relapse (HR, 0.86; P = .25), and overall mortality (HR, 0.90; P = .29) were not significantly different after MUD and MSD transplants. These data favor an MSD over a MUD in patients age ≥50 years.

Does younger donor age affect the outcome of reduced-intensity allogeneic hematopoietic stem cell transplantation for hematologic malignancies beneficially?

Sixty three patients aged 27-66 years (median 52) were allografted from HLA-matched sibling (n=47), 10 of 10 allele-matched unrelated (n=19), or one-antigen/allele-mismatched (n=7) donors aged 24-69 years (median 46) after a conditioning regimen comprising 100 mg/m(2) melphalan. Cyclophosphamide (50 mg/kg) was also administered to patients who had not been autografted previously. Cyclosporine or tacrolimus, and mycophenolate mofetil were administered to prevent graft-versus-host disease (GVHD). The 2-year cumulative incidences of relapse and TRM were 55 and 24% respectively, and 2-year probabilities of overall survival (OS) and disease-free survival (DFS) were 36 and 21%, respectively. Poor performance status, donor age >45 years and elevated lactate dehydrogenase (LDH) increased the risk of treatment-related mortality (TRM), refractory disease and donor age >45 years increased the risk of relapse, and OS and DFS were adversely influenced by refractory disease, poor performance status, increased LDH, and donor age >45 years. Our data suggest that younger donor age is associated with better outcome after sub-myeloablative allogeneic hematopoietic stem cell transplantation (HSCT) for hematologic malignancies due to lower TRM and relapse. This finding raises the question of whether a young 10-allele-matched unrelated donor is superior to an older matched sibling donor in patients where the clinical situation permits a choice between such donors.

In vivo analyses of early events in acute graft-versus-host disease reveal sequential infiltration of T-cell subsets

Graft-versus-host disease (GVHD) is a major obstacle in allogeneic hematopoietic cell transplantation. Given the dynamic changes in immune cell subsets and tissue organization, which occur in GVHD, localization and timing of critical immunological events in vivo may reveal basic pathogenic mechanisms. To this end, we transplanted luciferase-labeled allogeneic splenocytes and monitored tissue distribution by in vivo bioluminescence imaging. High-resolution analyses showed initial proliferation of donor CD4+ T cells followed by CD8+ T cells in secondary lymphoid organs with subsequent homing to the intestines, liver, and skin. Transplantation of purified naive T cells caused GVHD that was initiated in secondary lymphoid organs followed by target organ manifestation in gut, liver, and skin. In contrast, transplanted CD4+ effector memory T (T(EM)) cells did not proliferate in secondary lymphoid organs in vivo and despite their in vitro alloreactivity in mixed leukocyte reaction (MLR) assays did not cause acute GVHD. These findings underline the potential of T-cell subsets with defined trafficking patterns for immune reconstitution without the risk of GVHD.