Promising role of reduced-toxicity hematopoietic stem cell transplantation (PART-I)

Feasibility of thiotepa addition to the fludarabine-busulfan conditioning with tacrolimus/sirolimus as graft vs host disease prophylaxis

In classical reduced-intensity conditioning (RIC) regimens, including the fludarabine and busulphan (BF) combination, sirolimus and tacrolimus (SIR-TAC) as graft vs host disease (GVHD) prophylaxis has shown acceptable results. The outcomes of SIR-TAC in a more intense RIC regimen as Thiotepa-fludarabine-busulfan (TBF) have been hardly investigated. This retrospective study included all consecutive patients receiving an allogeneic hematopoietic stem cell transplantation for myeloid malignancies (January 2009-2017) conditioned with either TBF or BF and receiving SIR-TAC. Patients receiving TBF presented higher non-relapse mortality (31.6 vs 12.3%, p = .01), along with shorter overall survival (51.8% vs 77.8%, p < .01) at 2 years than patients treated with BF. There were no significant differences in the cumulative incidence of grade II-IV acute GVHD or moderate-severe chronic GVHD or relapse between both groups. These results suggest that TBF does not seem to improve the traditional RIC BF regimen, at least when associated with SIR-TAC prophylaxis.

Identifying risk factors associated with worse outcomes in adolescents and young adults undergoing hematopoietic stem cell transplantation

BACKGROUND

Adolescents and young adults (AYAs) undergoing allogeneic hematopoietic stem cell transplantation (HSCT) have unique risk factors and poor outcomes when compared to children, but this population has not been well studied. A hematopoietic stem cell transplantation-comorbidity index (HCT-CI) has been developed in adults to help predict outcomes, yet this index does not seem suitable for a younger population. Therefore, we sought to examine the prevalence of various risk factors in AYAs undergoing allogeneic HSCT and determine which factors had the greatest impact on overall survival (OS) and treatment-related mortality (TRM).

PROCEDURES

This was accomplished by retrospectively collecting data on 241 patients who received their first allogeneic HSCT at UCLA between 2005 and 2015. We investigated the effect of multiple predictors using the Cox proportional hazards model and Fine and Gray competing risk model for OS and TRM, respectively.

RESULTS

Our results showed that AYAs undergoing allogeneic HSCT had poor outcomes, with 5-year OS and NRM of 48% and 30%, respectively. We demonstrated that compared to a baseline model, the addition of the HCT-CI did not improve its ability to predict OS, while substituting individual comorbidities, that is, an unweighted comorbidity score, resulted in significant improvement in model performance. The factors associated with inferior outcomes were used to develop an AYA-specific risk score.

CONCLUSIONS

The comorbidities included in the HCT-CI as well as additional risk factors seen in younger populations need to be studied in prospective studies with the goal of validating and refining a risk score specific to AYA patients undergoing allogeneic HSCT.

Spiritual Well-Being in Hispanic and Non-Hispanic Survivors of Allogeneic Hematopoietic Stem Cell Transplantation

Research suggests that spiritual well-being positively contributes to quality of life during and following cancer treatment. This relationship has not been well-described in ethnically diverse survivors of allogeneic transplantation.  This study compares spiritual well-being and quality of life of Hispanic (n = 69) and non-Hispanic (n = 102) survivors. Hispanic participants were significantly younger and reported significantly greater spiritual well-being than non-Hispanic survivors. Survivors with higher spiritual well-being had significantly better quality of life. Meaning and Peace significantly predicted quality of life. Although Hispanic survivors report greater spiritual well-being, Meaning and Peace, irrespective of ethnicity, have a salutary effect on quality of life.

The efficacy and safety of a new reduced-toxicity conditioning with 4 days of once-daily 100 mg/m(2) intravenous busulfan associated with fludarabine and antithymocyte globulins prior to allogeneic stem cell transplantation in patients with high-risk myelodysplastic syndrome or acute leukemia

The optimal intensity of myeloablation associated with a reduced-toxicity conditioning (RTC) regimen in order to decrease the relapse rate without increasing non-relapse mortality (NRM), is not well established yet. This retrospective analysis was done on 30 patients with hematological malignancies. The aim was to assess the safety of a RTC regimen based on the busulfan at a dose of 100 mg/m(2)/d intravenously for 4 d, fludarabine at a dose of 30 mg/m(2)/d for 5 d, and anti-thymoglobulins at a dose of 2.5 mg/kg/d for 2 d. The cumulative incidences of grade 2-4 acute graft-versus-host disease (GVHD) and all grades chronic GVHD were 37% and 42%, respectively. Median 1-year overall survival and disease-free survival were 66% and 50%, respectively. At 1 year, the cumulative incidence of relapse/disease progression was 33%. NRM was 3% and 17% at day 100 and 1 year, respectively. This RTC conditioning regimen can lead to a long-term disease control. Moreover, it appears to be safe with a low NRM rate among high-risk patients.

Comparison of reduced-intensity and myeloablative conditioning regimens for allogeneic hematopoietic stem cell transplantation in patients with acute myeloid leukemia and acute lymphoblastic leukemia: a meta-analysis

Currently, the indications to perform reduced-intensity conditioning allogeneic hematopoietic stem cell transplant (RIC-HCT) are based on data derived mainly from large registry and single-centre retrospective studies. Thus, at the present time, there is limited direct evidence supporting the current practice in selecting patients with acute myeloid leukemia (AML) and acute lymphoblastic leukemia (ALL) for RIC versus myeloablative conditioning (MAC) transplants. To determine the relationship between dose intensity of conditioning regimen and survival outcomes after allografting in AML/ALL patients, we performed a meta-analysis of 23 clinical trials reported between 1990 and 2013 involving 15,258 adult patients that compare survival outcomes after RIC-HCT versus MAC-HCT. RIC-HCT resulted in comparable <2-year and 2-6 year overall survival (OS) rates post-transplantation even though the RIC-HCT recipients were older and had more active disease than MAC-HCT recipients. The 2-6 year progression-free survival (PFS), nonrelapse mortality, acute graft-versus-host disease (GvHD) and chronic GvHD rates were reduced after RIC-HCT, but relapse rate was increased. Similar outcomes were observed regardless of disease type and status at transplantation. Odds ratio for all outcomes remained comparable with or without performing separate analyses for the year of HCT and for retrospective versus prospective studies. Among RIC-HCT recipients, survival rates were superior if patients were in CR at transplantation. Significant inter-study heterogeneity for aGvHD data and publication bias for PFS data were observed. This meta-analysis showed no OS benefit of MAC-HCT over RIC-HCT across the entire cohort of patients suggesting that RIC-HCT could be an effective therapeutic option for AML/ALL patients who are ineligible for MAC-HCT and CR status is preferred before RIC-HCT.

The transfer of host MHC class I protein protects donor cells from NK cell and macrophage-mediated rejection during hematopoietic stem cell transplantation and engraftment in mice

Human hematopoietic stem cell engraftment has been studied extensively using xenograft transplant models with immunocompromised mice. It is standard practice to incorporate mouse models, such as the limiting dilution assay, to accurately assess the number of repopulating stem cells in bone marrow or umbilical cord blood collections or to confirm the long-term repopulating ability of cultured hematopoietic stem cells. In a previous study using a standard NOD/SCID mouse model to assess human hematopoietic stem cell engraftment we observed that all human cells had mouse MHC class I protein on their surface, suggesting that this is a mechanism adopted by the cells to evade host immune surveillance. To determine whether this was a xenograft phenomenon we studied host MHC transfer in an intraspecies mouse model and observed similar results. The transfer of MHC class I proteins has implications for antigen presentation and immune modulation. In this report, we used a standard mouse model of bone marrow transplantation to demonstrate that surface protein transfer between cells plays an important role in protecting donor hematopoietic cells from NK cell and macrophage-mediated rejection. The transfer of intact MHC class I antigens from host cells to transplanted donor cells confers a self identity on these otherwise foreign cells. This gives them the ability to evade detection by the host NK cells and macrophages. Once full donor chimerism is established, transplanted cells no longer require host MHC class I protein transfer to survive.

Indications and outcomes of reduced-toxicity hematopoietic stem cell transplantation in adult patients with hematological malignancies

Hematopoietic stem cell transplantation (HCT) utilizing non-myeloablative (NMA) and reduced-intensity conditioning (RIC) regimens (collectively referred to as reduced-toxicity HCT, RT-HCT) has become a viable therapeutic option for patients with hematological malignancies who are ineligible for standard myeloablative conditioning transplantation (MA-HCT). RT-HCT has been shown to induce stable engraftment with low toxicity, and to produce similar overall and progression-free survival (PFS) when compared to MA-HCT in acute myeloid leukemia and myelodysplastic syndrome. The best results for RT-HCT have been reported for patients with disease that is in remission, indolent and chemosensitive, and with a strong graft-versus-malignancy effect. Chronic graft-versus-host disease seems to correlate with a lower relapse rate and better PFS. RT-HCT is inferior when performed in poor risk or advanced disease, due to high relapse rates. A search for novel strategies that includes the most appropriate conditioning regimens and post-transplant immunomodulation protocols with more intensive anti-malignancy activity but limited toxicity is in progress. This review provides an update on the results of clinical studies of RT-HCT, and discusses possible indications and investigative strategies for improving the clinical outcomes of RT-HCT for the major hematological malignancies.