HLA-mismatched/haploidentical hematopoietic stem cell transplantation without in vitro T cell depletion for chronic myeloid leukemia: improved outcomes in patients in accelerated phase and blast crisis phase

Transplantation in CML in the TKI era: who, when, and how?

Molecular therapy with tyrosine kinase inhibitors (TKIs) has significantly reduced the indication for allogeneic hematopoietic stem cell transplantation (allo-HSCT) in chronic myeloid leukemia (CML). Treatment-free remission can be obtained in about 50% of patients with an optimal response. However, cure rates up to 90% are restricted to patients receiving HSCT. Timing is essential since HSCT in the early stages of the disease has the best outcome. Patients in a more advanced phase (AdP) than chronic-phase (chP) CML undergo HSCT with suboptimal outcomes, and the gap between chP and AdP disease is widening. First-line therapy should start with first- or second-generation (G) TKIs. Patients failing treatment (BCR-ABL1 transcripts of greater than 10% at 3 and 6 months and greater than 1% at 12 months) should be switched to second-line TKIs, and HSCT should be considered. Patients not responding to 2G-TKI therapy as well as patients in an accelerated phase (AP) or blast crisis (BC) are candidates for HSCT. Therapy resistant BCR-ABL1 mutations, high-risk additional cytogenetic abnormalities, and molecular signs of leukemia progression should trigger the indication for HSCT. Patients who, despite dose adjustments, do not tolerate or develop severe adverse events, including vascular events, to multiple TKIs are also candidates for HSCT. In AdP CML, TKIs do not show long-lasting results, and the outcome of HSCT is less optimal without pretransplant therapy. In these patients the induction of chP2 with TKIs, either alone (AP) or in combination with intensive chemotherapy (BC), followed by HSCT should be pursued.

Comparable clinical outcomes of haploidentical hematopoietic stem cell transplantation in patients with hepatitis-associated aplastic anemia and non-hepatitis-associated aplastic anemia

Hepatitis-associated aplastic anemia (HAAA), a rare subtype of aplastic anemia (AA), is defined as bone marrow failure occurring after acute hepatitis. Severe HAAA requires immunosuppressive therapy (IST) or hematopoietic stem cell transplantation (HSCT) as lifesaving treatment. The outcomes of HAAA patients who underwent haploidentical hematopoietic stem cell transplantation (haplo-HSCT) have not been systematically evaluated. We retrospectively compared the characteristics of 15 patients with HAAA and 60 non-hepatitis-associated aplastic anemia (non-HAAA) patients, all 75 of whom underwent haplo-HSCT in our hospital between January 2006 and October 2021. The median ages of the patients were 18 years old (range, 3-36) for HAAA patients and 13 years (range, 2-45) for non-HAAA patients (p = 0.693). The median time for neutrophil engraftment was 14 days (range, 11-22) in the HAAA group and 12 days (range, 10-21) in the non-HAAA group (p = 0.363). At the time of analysis, 15 HAAA patients and 58 non-HAAA patients were alive, and their median follow-up times were 37 (range, 3-87) months and 31 (range, 2-110) months (p = 0.347), respectively. There were no significant differences in the three-year overall survival (OS) rates (100% vs. 96.7 ± 0.33%, P = 0.638) or liver event-free survival (LEFS) (80.0 ± 0.17% vs. 76.7 ± 0.19%, P = 0.747) between the two groups. Despite the small number of HAAA patients due to the rarity of the disease, these results, such as the similar incidence rates of 3-year OS and fewer liver events than expected, suggest that haplo-HSCT is a feasible treatment for HAAA a when there are no human leukocyte antigen (HLA)-matched donors available and has a low risk of transplant-related mortality and complications.

Development and validation of a mortality predicting scoring system for severe aplastic anaemia patients receiving haploidentical allogeneic transplantation

Haploidentical allogeneic haematopoietic stem cell transplantation (haplo-HSCT) is a significant alternative treatment for severe aplastic anaemia (SAA). To improve this process by modifying the risk stratification system, we conducted a retrospective study using our database. 432 SAA patients who received haplo-HSCT between 2006 and 2020 were enrolled. These patients were divided into a training (n = 288) and a validation (n = 144) subset randomly. In the training cohort, longer time from diagnosis to transplantation, poorer Eastern Cooperative Oncology Group (ECOG) status and higher haematopoietic cell transplantation-specific comorbidity index (HCT-CI) score were independent risk factors for worse treatment-related mortality (TRM) in the final multivariable model. The haplo-HSCT scoring system was developed by these three parameters. Three-year TRM after haplo-HSCT were 6% [95% confidence interval (CI), 1-21%], 21% (95% CI, 7-40%), and 47% (95% CI, 20-70%) for the low-, intermediate-, and high-risk group, respectively (P < 0·0001). In the validation cohort, the haplo-HSCT scoring system also separated patients into three risk groups with increasing risk of TRM: intermediate-risk [hazard ratio (HR) 2·45, 95% CI, 0·92-6·53] and high-risk (HR 11·74, 95% CI, 3·07-44·89) compared with the low-risk group (P = 0·001). In conclusion, the haplo-HSCT scoring system could effectively predict TRM after transplantation.

Impact of ABO incompatibility on outcomes after haploidentical hematopoietic stem cell transplantation for severe aplastic anemia

The impact of ABO incompatibility on transplantation outcomes in severe aplastic anemia (SAA) patients receiving haploidentical hematopoietic stem cell transplantation (HSCT) remains controversial without published data. A total of 199 SAA patients receiving haploidentical HSCT from ABO-matched (n = 114), minor ABO-incompatible (n = 47), or major ABO-incompatible donors (n = 38) were included in this study. The median time and cumulative incidences of both myeloid and platelet engraftment in the ABO-compatible and ABO-incompatible groups were similar, and pure red cell aplasia was absent. Minor ABO incompatibility increased the rate of grade III-IV acute graft-versus-host disease (aGVHD) (ABO compatible: 6.14 ± 0.05%, minor incompatible: 19.15 ± 0.34%, and major incompatible: 10.53 ± 0.25%; P = 0.051), but did not influence the rates of grade II-IV aGVHD or chronic GVHD (cGVHD). Minor ABO-incompatibility was identified as an independent risk factor for grade III-IV aGVHD by multivariate analysis (hazard ration (HR) = 4.00 (1.48-10.80), P = 0.006). Chronic GVHD, mortality, and treatment failure were not increased in the minor ABO-incompatible group. For SAA patients receiving haploidentical HSCT, ABO compatible donors are better than ABO minor incompatible donors if several haploidentical donors are available.

Who is the best haploidentical donor for acquired severe aplastic anemia? Experience from a multicenter study

BACKGROUND

Haploidentical transplantation has been proposed as an effective treatment for severe aplastic anemia (SAA). The majority of patients have more than one HLA-haploidentical donor. Herein, we compared the outcomes between different donor-recipient relationships for optimal haploidentical donor selection in acquired SAA.

METHODS

We conducted a multicenter study based on a registered database of 392 patients with SAA treated with allogeneic hematopoietic stem cell transplantation (allo-HSCT) between 2006 and 2018. In total, 223 patients received grafts from father donors, 47 from mother donors, 91 from siblings, 29 from children, and 2 from collateral donors.

RESULTS

Of the 381 patients who survived more than 28 days, 379 (99.5%) recipients were engrafted. The 2-year overall survival (OS) was 86.6 ± 2.5%, 87.1 ± 4.9%, 84.3 ± 3.9%, and 92.2 ± 5.1% for recipients of father, mother, sibling, and child grafts, respectively, (P = 0.706). The 2-year failure-free survival (FFS) was 82.8 ± 2.7%, 86.7 ± 5.1%, 80.8 ± 4.2%, and 92.5 ± 5.1% for recipients of father, mother, sibling, and child grafts, respectively, (P = 0.508). There was no difference in the incidence of either acute or chronic graft-versus-host disease (GVHD) among the different donor sources in multivariate analyses. There were also no differences in the OS or FFS among the different donor sources in the Cox regression analysis. However, OS was significantly better in the patients with a shorter history of aplastic anemia (< 12 months), better performance status (ECOG scores 0-1), or moderate graft mononuclear cell (MNC) counts (6-10 × 10⁸/kg), and in female recipients with male donors. The FFS was also higher in patients with a shorter history of aplastic anemia (< 12 months) and better performance status (ECOG scores 0-1).

CONCLUSIONS

Fathers, mothers, siblings, and children are all suitable haploidentical donors for patients with SAA.

Therapeutic Outcomes of Haploidentical Allogeneic Hematopoietic Stem Cell Transplantation in Patients With Severe Aplastic Anemia: A Multicenter Study

BACKGROUND

Haploidentical donor (HID) allogeneic hematopoietic stem cell transplantation (HSCT) is an alternative curative treatment for patients with severe aplastic anemia (SAA) who do not have suitable matched related donors (MRD). The aim of this study was to compare the therapeutic outcomes of HID-HSCT with those of MRD-HSCT for SAA.

METHODS

A total of 235 SAA patients who underwent HID-HSCT (116) or MRD-HSCT (119) at 11 transplantation centers from January 2007 to January 2016 were included. Complications and survival outcomes were evaluated and compared between the 2 groups.

RESULTS

The HID group had a lower incidence of secondary graft failure but higher incidences of acute graft-versus-host disease (aGVHD) and chronic GVHD (cGVHD). However, the incidence of severe aGVHD (grades III-IV), poor graft function, and infections was comparable between groups. Patients in the HID group had a significantly lower survival and overall survival rates than those in the MRD group. The estimated 3-year survival rates for the MRD and HID groups were 82.82% and 75.00%, respectively. Ferritin levels, graft failure, poor graft function, severe aGVHD, and infections were the significant risk factors for survival.

CONCLUSIONS

The overall survival rate is acceptable for patients who underwent HID-HSCT, making it a feasible treatment choice for SAA patients.

Relationship of Cell Compositions in Allografts with Outcomes after Haploidentical Transplantation for Acquired Severe Aplastic Anemia: Effects of CD34+ and CD14+ Cell Doses

Background

The dose of certain cell types in allografts affects engraftment kinetics and clinical outcomes after allogeneic stem cell transplantation (SCT). Hence, the present study investigated the association of cell compositions in allografts with outcomes after unmanipulated haploidentical SCT (haplo-SCT) for patients with acquired severe aplastic anemia (SAA).

Methods

A total of 131 patients with SAA who underwent haplo-SCT were retrospectively enrolled. Cell subsets in allografts were determined using flow cytometry. To analyze the association of cellular compositions and outcomes, Mann-Whitney U nonparametric tests were conducted for patient age, sex, weight, human leukocyte antigen mismatched loci, ABO-matched status, patient ABO blood type, donor-recipient sex match, donor-recipient relationship, and each graft component. Multivariate analysis was performed using logistic regression to determine independent influence factors involving dichotomous variables selected from the univariate analysis.

Results

A total of 126 patients (97.7%) achieved neutrophil engraftment, and 121 patients (95.7%) achieved platelet engraftment. At 100 days after transplantation, the cumulative incidence of II-IV acute graft-versus-host disease (GVHD) was 32.6%. After a median follow-up of 842 (range: 124-4110) days for surviving patients, the cumulative incidence of total chronic GVHD at 3 years after transplantation was 33.7%. The probability of overall survival at 3 years was 83.0%. Multivariate analysis showed that higher total doses of CD14⁺ (P = 0.018) and CD34⁺ cells (P < 0.001) were associated with a successful platelet engraftment. A successful platelet was associated with superior survival (P < 0.001). No correlation of other cell components with outcomes was observed.

Conclusions

These results provide evidence and explain that higher doses of CD34⁺ and CD14⁺ cells in haploidentical allografts positively affect platelet engraftment, contributing to superior survival for patients with SAA.

Comparison of Different Conditioning Regimens of Haploidentical Hematopoietic Stem Cell Transplant in Patients With Acute Myeloid Leukemia

OBJECTIVES

We evaluated the safety and efficacy of 2 conditioning regimens (busulfan/fludarabine vs modified busulfan/cyclophosphamide) in patients with acute myeloid leukemia undergoing haploidentical hematopoietic stem cell transplant.

MATERAILS AND METHODS

Twenty patients with primary acute myeloid leukemia had been randomized into busulfan/fludarabine and modified busulfan/cyclophosphamide groups. We retrospectively compared hematopoietic engraftment, regimen-related toxicity, graft-versus-host disease, transplant-related mortality, leukemia-free survival, and overall survival between the groups.

RESULTS

All patients achieved engraftment with 100% donor chimerism. The median times for the neutrophil and platelet engraftment in the busulfan/fludarabine and modified busulfan/cyclophosphamide groups were 14.1 versus 14.3 days and 12.7 versus 12.2 days, respectively. Significantly lower incidences of pretreatment toxicity, blood transfusion, and virus activation were observed in the busulfan/fludarabine group. Acute grade 1 graft-versus-host-disease developed in all patients, which was successfully controlled with methylprednisolone. There were no significant differences in engraftment, graft-versus-host disease, leukemia-free survival, and overall survival between groups. Both of these conditioning regimens achieved stable engraftment. Regimen-related toxicity in the busulfan/fludarabine group was well tolerated compared with that in the modified busulfan/cyclophosphamide group, without an increase in relapse rate.

CONCLUSIONS

Our results demonstrated that myeloablative busulfan/fludarabine might be a highly effective and low-toxicity alternative for patients with acute myeloid leukemia.

Unmanipulated haploidentical transplantation conditioning with busulfan, cyclophosphamide and anti-thymoglobulin for adult severe aplastic anaemia

We conducted a retrospective analysis to evaluate outcomes of haploidentical transplantation in adult severe aplastic anaemia (SAA) patients. Fifty-one adults received haploidentical transplantation between May 2011 and December 2016. Patients were administered busulfan (Bu), cyclophosphamide (Cy) and anti-thymoglobulin (ATG) as conditioning regimens, followed by bone marrow and peripheral blood transplantation. The patients' median age was 25 years. Forty-nine patients survived for more than 28 days and all achieved donor myeloid engraftment. The median time for myeloid engraftment and platelet recovery was 13 days (range, 10-21) and 17.5 (range, 7-101) days. The cumulative incidence (CI) of grade II-IV and III-IV acute GvHD) was 20.00±0.33% and 6.00±0.12%, respectively. The incidence of chronic GvHD was 14.00±0.36% and 25.90±0.71%, and that of moderate-severe chronic GvHD was 2.51±0.06% and 6.92±0.25% at 1 and 3 years, respectively. The 3-year estimated overall survival and failure-free survival were both 83.5±5.4% with a median follow-up of 21.1 months. Multivariate analysis showed hematopoietic cell transplantation-specific comorbidity index (HCT-CI) score of ⩾3 was significantly associated with worse outcome. Haploidentical transplantation conditioning including Bu/Cy/ATG was a safe and effective strategy for adult SAA patients, and HCT-CI might be an outcome predictor in these patients.

Risk factors in patients undergoing haploidentical hematopoietic stem cell transplantation for high-risk childhood acute leukemia

In the present study, we sought to analyze the risk factors following haploidentical hematopoietic stem cell transplantation (haplo-HSCT) in children with high-risk acute leukemia. We retrospectively reviewed data from 73 children with high-risk leukemia. Univariate and multivariate analyses were performed to evaluate relationships between variables and patient outcomes. The mean time for neutrophil engraftment was significantly shorter in children given a graft with a higher number of nucleated cells (>10.13 × 108/kg vs ≤10.13 × 108/kg: 13.79 ± 2.73 vs 17.71 ± 3.90 days, P < 0.001) and in younger children (≤10 years vs >10 years: 14.21 ± 3.12 vs 17.71 ± 3.90 days, P < 0.001). Time to platelet engraftment was clearly shorter in children given a graft with higher number of nucleated cells (>10.13 × 108/kg vs ≤10.13 × 108/kg: 12.12 ± 8.62 vs 32.1 ± 24.83 days, P < 0.028). Overall survival was 64.6 ± 9.1%, 41.1 ± 10.1%, and 81.6 ± 9.6%, respectively, in children with HR-ALL in CR1, ALL in CR2-4, and AML (P = 0.012). The number of total nucleated cells was significantly associated with transplant-related mortality (TRM). We suggest that outcomes of haplo-HSCT may be improved by increased infusion of nucleated cells.

Transplantation from haploidentical donor is not inferior to that from identical sibling donor for patients with chronic myeloid leukemia in blast crisis or chronic phase from blast crisis

OBJECTIVES

Allogeneic hematopoietic stem cell transplantation (HSCT) is the only curative therapy for chronic myeloid leukemia (CML) patients in blast crisis (BC), and haploidentical donors (HID) are immediately available for most patients. We compared the outcomes of HID transplantation with those of matched related donor (MRD) transplantation in a cohort study.

PATIENTS AND METHODS

A total of 90 consecutive patients who received allogeneic HSCT because of CML-BC were investigated retrospectively. A total of 67 patients underwent transplantation from HID and 23 from MRD. Survival outcomes were compared between the two cohorts.

RESULTS

Of the 90 patients, 86 patients were engrafted. Three-year overall survival (OS) and relapse-free survival (RFS) were comparable between HID and MRD recipients (OS: 60.0% vs 55.3%, respectively, P=.580; RFS: 51.1% vs 47.8%, respectively, P=.512). Three-year incidences of transplant-related mortality (TRM) and relapse did not differ between HID and MRD recipients (relapse: 21.0% vs 26.1%, respectively, P=.626; TRM: 27.9% vs 26.1%, respectively, P=.937). In multivariate analyses, previous chemotherapy history and not achieving CHR before HSCT are independent adverse predictors of OS.

CONCLUSIONS

For CML-blast crisis or chronic phase from blast crisis patients, HID transplantation achieves comparable survival to MRD transplantation. HID donors can be regarded as regular donors for these special patients at selected centers.

Haplo-identical transplantation for acquired severe aplastic anaemia in a multicentre prospective study

We conducted a prospective, multicentre study to confirm the feasibility of haplo-identical transplantation in treatment of severe aplastic anaemia (SAA) as salvage therapy, by analysing the outcomes of 101 patients who received haplo-identical transplantation between June 2012 and October 2015. All cases surviving for more than 28 d achieved donor myeloid engraftment. The median time for myeloid engraftment was 12 (range, 9-25) days and 15 (range, 7-101) days for platelets, with a cumulative platelet engraftment incidence of 94·1 ± 0·1%. With a median follow-up of 18·3 (3·0-43·6) months, recipients from haplo-identical transplantation had more cumulative incidence of grade II-IV acute graft-versus-host disease (aGVHD, 33·7% vs. 4·2%, P < 0·001), more chronic GVHD (22·4% vs. 6·6%, P = 0·014) at 1 year, but similar grade III-IV aGVHD (7·9% vs. 2·1%, P = 0·157), 3-year estimated overall survival (OS, 89·0% vs. 91·0%, P = 0·555) and failure-free survival (FFS, 86·8% vs. 80·3%, P = 0·659) when compared with 48 patients who received contemporaneous transplantation from matched related donors. Multivariate analysis showed no significant difference in engraftment and survival between the two cohorts. Both OS and FFS for the entire population correlated significantly with grades III-IV aGVHD. In conclusion, haplo-identical transplantation is a feasible choice for SAA with favourable outcomes.

How do we choose the best donor for T-cell-replete, HLA-haploidentical transplantation?

In haploidentical stem cell transplantations (haplo-SCT), nearly all patients have more than one donor. A key issue in the haplo-SCT setting is the search for the best donor, because donor selection can significantly impact the incidences of acute and chronic graft-versus-host disease, transplant-related mortality, and relapse, in addition to overall survival. In this review, we focused on factors associated with transplant outcomes following unmanipulated haplo-SCT with anti-thymocyte globulin (ATG) or after T-cell-replete haplo-SCT with post-transplantation cyclophosphamide (PT/Cy). We summarized the effects of the primary factors, including donor-specific antibodies against human leukocyte antigens (HLA); donor age and gender; killer immunoglobulin-like receptor-ligand mismatches; and non-inherited maternal antigen mismatches. We also offered some expert recommendations and proposed an algorithm for selecting donors for unmanipulated haplo-SCT with ATG and for T-cell-replete haplo-SCT with PT/Cy.

Allogeneic Stem Cell Transplantation for Patients with T315I BCR-ABL Mutated Chronic Myeloid Leukemia

Allogeneic stem cell transplantation (SCT) is currently the only curative treatment option for chronic myeloid leukemia (CML) patients with BCR-ABL T315I mutations. We report the outcome of SCT in 22 patients with T315I(+) CML, most (n = 16) from haploidentical family donors (HID-SCT). At the time the mutation was detected, 8 patients were in the chronic phase (CP), 7 in the accelerated phase (AP), and 7 in the blast phase (BP). At the time of SCT 7 were in the CP, 8 in the AP or returning to the CP post-AP (AP/AP-CPn), and 7 in the BP or returning to CP post-BP (BP/BP-CPn). The cumulative incidence of grades III to IV acute graft-versus-host disease was 9.1%. Chronic graft-versus-host disease was observed in 60.0% of patients, including 25.0% who suffered from severe disease. Four patients died of transplant-related complications at a median interval from SCT of 16.3 months. The estimated 2-year leukemia-free survival rate was 80.0%, 72.9%, and 0% in CP, AP/AP-CPn and BP/BP-CPn groups at the time of SCT, respectively. After a median follow-up of 17.3 months from SCT, 14 patients are alive, including 13 in complete molecular response and 1 with an extramedullary relapse. In conclusion, HID-SCT is a potentially curative treatment for T315I + CML patients. For patients in CP/AP, immediate SCT might result in promising survival. The outcome of patients in BP with T315I(+) mutation remains very poor.

Management of Elderly Patients with Newly Diagnosed Chronic Myeloid Leukemia in the Accelerated or Blastic Phase

In the elderly population, the accelerated and blastic phases of chronic myeloid leukemia (CML) are difficult to treat, not just because of the higher chance of acquired mutations than in younger individuals, but because of additional associated co-morbidities. Tyrosine kinase inhibitors are well-established in the treatment of the chronic phase of CML, and their use in advanced phases is ever-increasing. Elderly patients who are still eligible candidates for transplant can undergo reduced-intensity transplants from related or unrelated donors after reverting to chronic phase. Post-transplantation, these patients require adequate monitoring and therapy to prevent relapses. Newer modalities of treatment or interventions are urgently required in this complex group of patients.

Management of advanced-phase chronic myeloid leukemia

The management of chronic myeloid leukemia (CML) in accelerated or blast phase (advanced phase) remains a significant challenge despite the introduction of very effective tyrosine kinase inhibitors (TKIs). The biology of advanced-phase CML is complex and engages several pathways that are not optimally targeted by TKIs. Allogeneic stem cell transplantation remains the only potentially curative therapy, but the effectiveness of this conventional approach is limited. New strategies are required to improve the outlook for these patients.

Superiority of allogeneic hematopoietic stem cell transplantation to nilotinib and dasatinib for adult patients with chronic myelogenous leukemia in the accelerated phase

In the tyrosine kinase inhibitor (TKI) era, imatinib is the first-line therapy for patients with chronic myeloid leukemia (CML) in chronic or accelerated phase. Although second-generation TKIs (TKI2), including dasatinib and nilotinib, are appropriate treatment regimens for patients with disease that progressed to accelerated phase following imatinib therapy, allogeneic hematopoietic stem cell transplantation (allo-HSCT) is the only curative therapy. This study retrospectively analyzed the efficacy of TKI2 and HSCT for treatment of CML in accelerated phase. Ninety-three patients with CML registered in the Chinese CML alliance database from February 2001 to February 2014 were enrolled and divided into the TKI2 (n = 33) and allo-HSCT (n = 60) groups. In the TKI2 group, 26 and 7 patients received nilotinib and dasatinib, respectively, as initial TKI2 and 11 patients transferred to the alternative TKI2 after failure to one TKI2. In the allo-HSCT group, 22 (36.7%), 35 (58.3%), and 3 (10%) patients underwent allo-HSCT from an HLA-matched sibling donor, HLA mismatched/haploidentical donor, and unrelated donor, respectively. All patients in the HSCT group were engrafted. Overall, 69.7%, 48.5%, and 45.5% of patients presented hematological, cytogenetic, and major molecular responses, respectively, to at least one of TKI2. All 60 patients (100%) achieved CHR and cytogenetic response in the HSCT group. Patients in the TKI2 group exhibited lower 5-year overall survival rate (42.9% vs. 86.4%, P = 0.002), 5-year event-free survival rate (14.3% vs. 76.1%, P < 0.001), and 5-year progression-free survival (28.6% vs. 78.1%, P < 0.001) than those in the allo-HSCT group. Multivariate analysis showed that male sex and TKI2 therapy were predictors of poor overall survival, whereas hemoglobin < 100 g/L and TKI2 therapy were predictors of poor event-free survival and progression-free survival. These results indicated that allo-HSCT may be superior to nilotinib and dasatinib for adult patients with CML in accelerated phase.

An overview of conditioning regimens for haploidentical stem cell transplantation with post-transplantation cyclophosphamide

Haploidentical related donors are an attractive alternative source of stem cells for allogeneic stem cell transplantation due to widespread availability and ease of stem cell procurement. Historically, haploidentical stem cell transplantation (HaploSCT) with extensive T-cell depletion has been associated with high rates of infectious complications and nonrelapse mortality (NRM). Post-transplantation cyclophosphamide (PTCy) has been shown to induce immune tolerance, effectively control graft-versus-host-disease (GVHD), and is associated with lower NRM, making it a preferred option for patients undergoing HaploSCT. Over the last decade, several groups investigated PTCy for GVHD prevention in HaploSCT; it is now successfully utilized with both myeloablative and nonmyeloablative conditioning regimens with survival comparable to HLA-matched transplantation. Future directions will focus on optimizing conditioning regimens by diagnosis, improving donor selection, and enhancing graft-versus-leukemia effect.

An update on allogeneic hematopoietic progenitor cell transplantation for myeloproliferative neoplasms in the era of tyrosine kinase inhibitors

Myeloproliferative neoplasms are a category of diseases that have been traditionally amenable to allogeneic hematopoietic progenitor cell transplantation. Current developments in drug therapy have delayed transplantation for more advanced phases of the disease, especially for patients with CML, whereas transplantation remains a mainstream treatment modality for patients with advanced myelofibrosis and chronic myelomonocytic leukemia. Reduced-intensity conditioning has decreased the treatment-related mortality, and advances in the use of alternative donors for transplantation could extend the use of this procedure to an increasing number of patients with improved safety and efficacy. Here we review the current knowledge about allogeneic transplantation for myeloproliferative neoplasms and discuss the most important aspects to be considered when contemplating transplantation for patients with these diseases. Janus kinase 2 inhibitors offer the promise to improve spleen size and performance of patients with myelofibrosis and extend transplantation for patients with more advanced disease.

HLA and KIR genotyping correlates with relapse after T-cell-replete haploidentical transplantation in chronic myeloid leukaemia patients

Background:

Conflicting results have been reported regarding the predicative roles of alloreactive natural killer (NK) cells on the outcomes of transplantation in leukaemia patients.

Methods:

We prospectively analysed the human leukocyte antigen (HLA) typing of donor–recipient pairs and the KIR typing of the donors in 97 CML patients to address the predictive roles of NK cells in relapse undergoing T-cell-replete haploidentical transplantation.

Results:

Patients with class I ligands for the donor-inhibitory KIR gene exhibited decreased molecular and haematologic relapse rates (P=0.003 and P=0.015, respectively). There was a significantly reduced risk of molecular and haematologic relapse in patients with HLA-C1C2 or C2C2 who accepted donors with KIR2DS1 or in patients with HLA-Bw4 who accepted donors with KIR3DS1 (‘recipient with relevant KIR ligand for donor-activating KIR', n=25), compared with the remaining transplants (n=72, P=0.009 and P=0.009, respectively). In addition, the presence of class I ligand in the recipients of donor-activating KIR contributed to a decreased relapse rate in patients lacking class I ligand in the recipient of donor-inhibitory KIR (P=0.04 and P=0.03, respectively).

Conclusions:

This study suggests that the presence of class I ligands for the donor-activating or donor-inhibitory KIR gene in the recipient might confer some protection against leukaemic relapse in T-cell-replete haploidentical transplantation.

EBMT risk score can predict the outcome of leukaemia after unmanipulated haploidentical blood and marrow transplantation

Systematic, standardised pretransplant risk assessment is an important tool for predicting patient outcomes following allogeneic haematopoietic SCT (HSCT). To assess the European Group for Blood and Marrow Transplantation (EBMT) risk score capacities for predicting patient outcomes following unmanipulated haploidentical blood and marrow transplantation (HBMT), we analysed 502 leukaemia patients who received transplants at our centre between 2008 and 2010. The cohort OS and leukaemia-free survival (LFS) were 72.1% and 68.1%, whereas the cumulative non-relapse mortality (NRM) and relapse incidences were 16.5% and 16.1%. According to univariate analysis, the values for OS, LFS and NRM were worse for an EBMT risk score of 6 (40.0, 40.0, 50.0%) than a score of 1 (83.1, 78.3, 8.4%). Hazard ratios steadily increased for each additional score point. Likewise, a higher EBMT risk score was associated with an increased relapse incidence. Importantly, the EBMT risk score prognostic value regarding OS, LFS, NRM and relapse was maintained in the multivariate analysis. Moreover, we also made a haploidentical EBMT (haplo-EBMT) risk score, which used number of HLA disparity instead of donor type, and the haplo-EBMT risk scores can also be used to predict patient outcomes following unmanipulated HBMT.

HLA-haploidentical hematopoietic SCT from collateral related donors without in vitro T-cell depletion for hematological malignancies

HLA-haploidentical hematopoietic SCT (HSCT) provides an opportunity for almost all patients who lack HLA-matched sibling donors. The donor availability can be increased by including the collateral related donors (CRDs). We compared clinical outcomes of patients with hematological malignancies, who underwent haploidentical HSCT from CRD (n=30) and immediate related donors (IRDs; n=120). In CRDs, 29 (96.7%) patients achieved sustained engraftment. In CRDs and IRDs, the median times of myeloid recovery were 13 (range 10-20 days) and 14 days (range 12-23 days), and the median times of platelet recovery were 18 (range 7-270) and 15 days (range 7-132 days; P=0.027). The incidences of II-IV acute GVHD were 27.6% versus 39.4% (P=0.058). The 2-year cumulative incidences of chronic GVHD (cGVHD) were 63.3% versus 57.8% (P=0.365). The 2-year incidence of extensive cGVHD of CRDs was significantly higher than that of IRDs (36.7% versus 20.2%, P=0.03). The 2-year incidences of relapse, 3-year probability of OS and leukemia-free survival for the two groups were 26.7% versus 14.8% (P=0.17), 56.7% versus 70.4% (P=0.224) and 50.0% versus 65.4% (P=0.103), respectively. This study shows that haploidentical HSCT from CRDs can provide a safe and effective treatment for patients with hematological malignancies. CRDs could be an alternative when there was no suitable IRDs.

Advancement of human leukocyte antigen-partially matched related hematopoietic stem cell transplantation

Allogeneic hematopoietic stem cell transplantation (HSCT) is one of the most effective options for hematological malignancies, and human leukocyte antigen-partially matched related donors (PMRDs) are a valuable option for HSCT. Several protocols (with or without ex vivo T-cell depletion (TCD)) have been established worldwide. TCD including CD34(+) positive selection and CD3/CD19 depletion has successfully overcome the human leukocyte antigen disparity. However, TCD is associated with prolonged immune deficiencies, increased risks of infectious complications, and high transplantation-related mortality. PMRD HSCTwithout ex vivo TCD is well developed, and numerous patients have benefitted from it. Here, we review the literature on PMRD HSCT.

Allogeneic stem cell transplantation for chronic myeloid leukemia

In recent years new, more potent tyrosine-kinase inhibitors have been introduced to accompany imatinib for the treatment of chronic myeloid leukemia. Most patients in chronic phase obtain an optimal response to these oral agents with minimal toxicity. Allogeneic stem cell transplantation is therefore indicated only in a minority of patients who do not achieve an adequate response to first, second or third generation agents. Patients in accelerated phase have a lower chance of achieving an optimal response on these drugs. For patients in blast phase, transplantation remains the only therapy with curative potential, although now it is increasingly used in combination with tyrosine-kinase inhibitors. In this review we address the role of allogeneic stem cell transplantation in the treatment of this disease and how patients should be transplanted.

Allogeneic hematopoietic stem cell transplantation in China: where we are and where to go

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is an effective and sometimes the only curative therapy for patients with certain hematological diseases. Allo-HSCT has been practiced in China for approximately 30 years, and great improvements have been made within the past decade, particularly in fields such as the haploidentical HSCT system, strategies to overcome relapse and GVHD, and modified HSCT for elderly patients. This review will describe the current situation and provide a prospective of these unique aspects of Allo-HSCT in China.

The effect of HLA disparity on clinical outcome after HLA-haploidentical blood and marrow transplantation

The relative importance of various human leukocyte antigen (HLA) loci has not been established for unmanipulated HLA-mismatched/haploidentical transplantation. To address this question, we analyzed the impact of HLA-A, HLA-B, HLA-DRB1, HLA-DRB3, HLA-DRB4, and HLA-DRB5 on the outcome of HLA-haploidentical transplantation. Four hundred and eighty-one donor-recipient pairs were fully typed before transplantation. In univariate analysis, HLA-B mismatch not only demonstrated significant adverse effects on acute graft-versus-host disease (GVHD) and transplant-related mortality but also was associated with reduced overall survival and leukemia-free survival (LFS). In multivariate analysis, HLA-B mismatch remained the independent risk factor for acute GVHD and transplant-related mortality. The high risk of disease and the female donor were found to be significant factors for reduced overall survival and LFS. Furthermore, multiple mismatch of the HLA locus was found to have no synergistic adverse effect on outcomes. Our results suggest that prospective matching of patients and donors for HLA-B antigen in the unshared HLA haplotype is warranted for HLA-mismatched/haploidentical transplantation.

Haploidentical/mismatched hematopoietic stem cell transplantation without in vitro T cell depletion for T cell acute lymphoblastic leukemia

The outcome of T cell acute lymphoblastic leukemia (T-ALL) is poorly understood. Allogeneic hematopoietic stem cell transplantation (HSCT) remains 1 of the best options to cure T-ALL. However, many patients cannot find an HLA-matched donor. Our institute established a new protocol for haplo-identical HSCT. Busulfan, cyclophosphamide, cytosine arabinoside, and methyl CCNU plus antithymocyte globulin was used for conditioning therapy. Seventy-two patients diagnosed with T-ALL underwent transplantation from haploidentical donor family members. The incidence rates of grades II to IV acute graft-versus-host disease (aGVHD) and of grades III and IV aGVHD were 49% ± 12% and 19% ± 12%, respectively. The cumulative incidence rate for chronic GVHD (cGVHD) at 2 years after HSCT was 41% ± 12%. After a median follow-up of 12 months, 15 patients had relapsed, 14 died from relapse, and 41 patients were still alive without disease recurrence. The probability of leukemia-free survival (LFS) was 44.2% ± 7.4% at 3 years. Patients transplanted during their first complete remission (CR1) had a lower relapse rate (18.8% versus 37.5%, P = .049, with a relative risk [RR] = 0.247, P = .007), a lower nonrelapse mortality (NRM) rate (16.6% versus 50.0%, P = .046, with an RR = 0.279, P = .024), and better LFS (54.8% versus 12.5%, P = .001, with an RR = 0.315, P = .004) compared with patients transplanted beyond CR1. This study confirmed that haploidentical/mismatched HSCT could be an alternative treatment choice for T-ALL.

Controversies in the treatment of CML in children and adolescents: TKIs versus BMT?

Chronic myeloid leukemia (CML) is a relatively rare hematopoietic malignancy in the pediatric and adolescent population. This makes it difficult to perform clinic trials that can define the best therapeutic option when considering the impact of tyrosine kinase inhibitors (TKIs) versus the established approach of allogeneic hematopoietic cell transplantation (HCT). With the relatively low toxicity of TKIs, there are little data regarding when HCT or long-term TKI therapy is a better option. There are even less data regarding the duration of TKI treatment in the pediatric CML in chronic phase (CML-CP) patients who may receive over 60 years of therapy. As children and adolescent are treated for longer times with TKIs, it has become clear that toxicities may make long-term TKI therapy less attractive compared to allogeneic HCT. HCT has the long-term complications of growth failure, infertility, chronic graft-versus-host disease (GVHD), metabolic syndrome, and secondary malignancies, whereas prolonged TKIs may cause growth failure, hepatic, and cardiac complications. Moreover, HCT is a potentially curative intervention, whereas TKI is not curative, requiring prolonged exposure. In this article, we discuss the relative merit of the 2 therapeutic approaches and recommend that all children and adolescents with CML-CP should initially be treated with imatinib and maintained with TKI therapy indefinitely if there is a good response. We recommend that allogeneic HCT with an HLA-identical sibling donor or closely matched unrelated donor be considered for patients with treatment failure or recurrence after receiving salvage second-generation TKI treatment. We also conclude that randomized international trials are urgently needed to evaluate the best therapies for pediatric CML.

Imatinib mesylate versus allogeneic hematopoietic stem cell transplantation for patients with chronic myelogenous leukemia in the accelerated phase

The relative merits of allogeneic hematopoietic stem cell transplantation (allo-HSCT) and imatinib for chronic myelogenous leukemia in the accelerated phase (AP-CML) have not previously been evaluated. This cohort study was designed to compare the outcomes of imatinib (n = 87) versus allo-HSCT (n = 45) for AP-CML. A multivariate analysis of the total population revealed that a CML duration ≥ 12 months, hemoglobin < 100 g/L, and peripheral blood blasts ≥ 5% were independent adverse prognostic factors for both overall survival (OS) and progression-free survival (PFS). Both treatments resulted in similar survival in low-risk (no factor) patients, with 6-year event-free survival (EFS), OS, and PFS rates of more than 80.0%. Intermediate-risk (any factor) patients showed no difference in EFS and OS, but 6-year PFS rates were 55.7% versus 92.9% (P = .047) with imatinib versus allo-HSCT, respectively. Among high-risk (at least 2 factors) patients, imatinib was by far inferior to allo-HSCT, with 5-year EFS, OS, and PFS rates of 9.3% versus 66.7% (P = .034), 17.7% versus 100% (P = .008), and 18.8% versus 100% (P = .006), respectively. We conclude that allo-HSCT confers significant survival advantages for high- and intermediate-risk patients with AP-CML compared with imatinib treatment; however, the outcomes of the 2 therapies are equally good in low-risk patients. All trials were registered with the Chinese Clinical Trial Registry (www.chictr.org) as CHiCTR-TNC-10000955.

Unmanipulated HLA-mismatched/haploidentical blood and marrow hematopoietic stem cell transplantation

Extensive ex vivo T cell-depleted or unmanipulated haploidentical transplantation provides benefits of rapid and near universal donor availability for patients without HLA-identical sibling donors or those who urgently need transplant. However, CD34 selected haplotype mismatched transplantation was limited by delayed immune reconstitution (IR), although this protocol has now been an acceptable approach. Recently, Peking University researchers developed a novel approach to HLA-mismatched/haploidentical blood and marrow transplantation without in vitro T cell depletion (GIAC protocol). This review summarizes transplant outcomes, and factors correlating with transplant outcomes following the GIAC protocol. Moreover, future challenges in improving posttransplant IR and finding the best approach reducing the incidence and severity of GVHD, whereas preserving graft-versus-leukemia effect to prevent the recurrence of underlying malignancy, are also discussed.

HLA-mismatched hematopoietic SCT without in vitro T-cell depletion for myelodysplastic syndrome

Allogeneic hematopoietic SCT (HSCT) is currently the only curative treatment for myelodysplastic syndrome (MDS). However, many patients cannot find an HLA-matched donor. We have developed a new protocol for HLA-mismatched (including haploidentical) HSCT using G-CSF-primed BM plus G-CSF-mobilized PBSCs without in vitro T-cell depletion. A total of 36 patients diagnosed with high-risk MDS (RAEB (refractory anemia with excess blasts) or RAEBt (RAEB in transformation)) underwent transplantation from HLA-mismatched family donors. All patients achieved sustained myeloid engraftment. The cumulative incidence of grades II-IV acute GVHD (aGVHD) was 60% and that of grades III and IV aGVHD was 15%. The 2-year cumulative incidence of chronic GVHD was 56%. After a median follow-up of 17 months, 4 patients had relapsed and died and 25 patients were still alive. The 2-year probability of leukemia-free survival (LFS) was 65%. Patients transplanted within 7 months of diagnosis had better LFS (89 vs 43% ). Severe aGVHD decreased the LFS significantly by increasing non-relapse mortality (NRM). This study confirms that HLA-mismatched HSCT is a treatment option for MDS. Patients with high-risk MDS benefit from receiving HSCT early in the course of the disease.

The impact of CD34+ cell dose on platelet engraftment in pediatric patients following unmanipulated haploidentical blood and marrow transplantation

OBJECTIVE

Unmanipulated haploidentical blood and marrow transplantation has been developed as an alternative transplant strategy for pediatric patients with hematological diseases. The aim of this study was to investigate the effects of donor and recipient characteristics on hematopoietic recovery in pediatric patients following unmanipulated haploidentical transplantation.

METHODS

Factors correlating with hematopoietic recovery in 133 pediatric patients after unmanipulated haploidentical transplantation were analyzed retrospectively.

RESULTS

All patients reached an absolute neutrophil count of 500/microl in a median of 12 days (range, 9-49 days). One hundred thirty-three patients reached an untransfused platelet count of more than 20,000/microl in a median of 15 days (range, 7-180 days). Univariate analysis showed five factors associated with platelet engraftment. These were time to transplantation after diagnosis (P = 0.072), infused nuclear cells/kg of recipient weight (P = 0.028), CD3+ cells/kg of recipient weight (P = 0.082), CD4+ cells/kg of recipient weight (P = 0.083), and CD34+ cells/kg of recipient weight (P = 0.012). Multivariate analysis showed that infused CD34+ cells/kg of recipient weight (CD34+ cells more than 2.42 x 10(6)/kg vs. less than or equal to 2.42 x 10(6)/kg, HR = 1.733; 95% CI 1.222-2.549; P = 0.002) were significantly associated with an increased risk of platelet engraftment. Patients receiving a CD34+ cell dose more than 2.42 x 10(6)/kg had a short time [12 days (range, 7-176 days)] to achieve an untransfused platelet engraftment, compared to 18 days (range, 7-180 days) in patients receiving a lower dose (P < 0.001).

CONCLUSIONS

Our results suggest that low number of CD34+ cells in allografts is a critical factor associated with delayed platelet engraftment after unmanipulated haploidentical transplantation in pediatric patients.

Influence of lymphocyte recovery on outcome of haploidentical transplantation for hematologic malignancies

Unmanipulated human leukocyte antigen (HLA)-mismatched/haploidentical blood and marrow transplantation is an established treatment for patients without HLA-matched related or unrelated donors. However, the prognostic significance of early lymphocyte recovery in this transplant setting is not defined. In this study, we investigated the association of day 30 absolute lymphocyte count (ALC-30) with outcome after unmanipulated HLA-mismatched/haploidentical transplantation. We prospectively analyzed the relationship between ALC-30 and transplant outcomes in 206 patients with hematologic malignancies receiving T-cell-replete transplantation from HLA-mismatched/haploidentical related donors. Multivariate analysis showed that ALC-30 above the cutoff value of 300 cells/microL was associated with improved overall survival (hazard ratio [HR], 0.258; 95% confidence interval [CI], 0.141-0.472; p < 0.0001); improved cancer-free survival (HR, 0.289; 95% CI, 0.166-0.501; p < 0.0001); reduced relapse (HR, 0.370; 95% CI, 0.161-0.853; p = 0.020); and decreased transplant-related mortality (HR, 0.211; 95% CI, 0.097-0.457; p < 0.0001). Our results suggest that the recovery of ALC-30 might have an influence on transplant outcomes following unmanipulated HLA-mismatched/haploidentical transplantation.

Microfluidic chip-based assay for post-hematopoietic stem cell transplantation chimerism monitoring using polymorphic tandem repeat markers

Following hematopoietic stem cell transplantation (HSCT), it is important to determine whether engraftment is successful and to track the dynamic changes of the graft. Tandem repeats such as minisatellites and microsatellites are currently the most established markers for chimerism application. We have developed a reliable method to quantitatively evaluate engraftment status in post-allogeneic HSCT patients using variable number of tandem repeat (VNTR) markers and "lab-on-a-chip" microfluidic electrophoresis technology. Following identification of an informative marker by conventional polymerase chain reaction (PCR), donor chimerism percentage was calculated based on a standard curve generated from artificially mixed patient-donor DNA-specific alleles in serial dilutions. All PCR products were mixed with commercial gel dye and loaded into Agilent DNA 1000 microfluidic LabChips for DNA sizing and quantitation. In 44 patients, separation of pretransplant and donor DNA fragments was resolved clearly and accomplished rapidly within 30min. Chimerism analysis using this platform is able to detect an amount as low as 6.3% donor DNA with acceptable coefficient of variation values. We also demonstrated concordant chimerism analysis findings using both microchip tandem repeats and real-time PCR quantitation of insertion-deletion polymorphisms. This microchip platform obviates the need for fluorescently labeled primers or any post-PCR sample manipulation. Quantitative monitoring of post-HSCT chimerism status using microfluidic electrophoresis is a useful tool for both large- and small-scale post-HSCT chimerism centers.

Current status of haploidentical stem cell transplantation for leukemia

Haploidentical hematopoietic stem cell transplantation has made tremendous progress over the past 20 years and has become a feasible option for leukemia patients without a HLA identical sibling donor. The early complications of severe graft-versus-host disease (GVHD), graft failure and delayed engraftment, as well as disease recurrence have limited the use of this approach. Newer strategies have been applied and overcome some of the problems, including the use of T-cell depleted graft, "mega" dose of stem cells, intensive post-transplant immunosuppression and manipulation of the graft. These have decreased the transplant related mortality and GVHD associated with haploidentical transplantation, however, the major problems of disease relapse and infection, which related to late immune reconstitution, limit the development of haploidentical HSCT. Future challenges remain in improving post-transplant immune reconstitution and finding the best approach to reduce the incidence and severity of GVHD, while preserving graft-versus-leukemia effect to prevent the recurrence of underlying malignancy.