Unmanipulated Haploidentical Hematopoietic Stem Cell Transplantation in First Complete Remission Can Abrogate the Poor Outcomes of Children with Acute Myeloid Leukemia Resistant to the First Course of Induction Chemotherapy

Sub-myeloablative Second Transplantations with Haploidentical Donors and Post-Transplant Cyclophosphamide have limited Anti-Leukemic Effects in Pediatric Patients

Pediatric patients with high-risk hematologic malignancies who experience relapse after a prior allogeneic hematopoietic cell transplant (HCT) have an exceedingly poor prognosis. A second allogeneic HCT offers the potential for long-term cure but carries high risks of both subsequent relapse and HCT-related morbidity and mortality. Using haploidentical donors for HCT (haploHCT) can expand the donor pool and potentially enhance the graft-versus-leukemia effect but is accompanied by a risk of graft-versus-host disease (GVHD). The goal of this protocol was to intensify the antileukemia effect of haploHCT for pediatric patients with hematologic malignancies that relapsed after prior allogeneic HCT, while limiting regimen-associated toxicities. This phase II clinical trial evaluated a sub-myeloablative preparative regimen consisting of anti-thymocyte globulin, clofarabine, cytarabine, busulfan, and cyclophosphamide, in combination with plerixafor to sensitize leukemic blasts. Participants received a mobilized peripheral blood unmanipulated haploidentical donor graft with one dose of post-transplant cyclophosphamide as GVHD prophylaxis, followed by natural killer (NK) cell addback. Here we report the clinical outcomes and immune reconstitution of 17 participants treated on the study and 5 additional patients treated on similar single-patient treatment plans. Of the 22 participants analyzed, 12 (55%) had active disease at the time of HCT. The regimen provided robust immune reconstitution, with 21 participants (95%) experiencing neutrophil engraftment at a median of 14 days after HCT. In this high-risk population, the overall survival was 45% (95% confidence interval [CI], 24%-64%), with a 12-month event-free survival of 31% (95% CI, 14%-51%) and cumulative incidence of relapse at 12 months of 50% (95% CI, 27%-69%). Four participants (18%) remain in remission at >5 years follow-up. Expected HCT-related organ-specific toxicities were observed, and 13 participants (59%) experienced acute or chronic GVHD. This intensified but sub-myeloablative regimen, followed by a high-dose unmanipulated haploidentical graft, post-transplantation cyclophosphamide, and NK cell infusion, resulted in adequate immune reconstitution but failed to overcome the elevated risks of relapse and treatment-related morbidity in this high-risk population.

Contemporary haploidentical stem cell transplant strategies in children with hematological malignancies

The barriers to HLA-mismatched or haploidentical hematopoietic stem cell transplantation (HSCT), namely GvHD and graft failure, have been overcome with novel transplant platforms. Post-transplant Cyclophosphamide (PTCy) is widely available, feasible and easy to implement. TCRαβ T and B cell depletion comes with consistent GvHD preventive benefits irrespective of age and indication. Naive T-cell depletion helps prevention of severe viral reactivations. The Beijing protocol shows promising outcomes in patients with poor remission status at the time of transplantation. For children, the toxicities and late outcomes related to these transplants are truly relevant as they suffer the most in the long run from transplant-related toxicities, especially chronic GvHD. While comparing the outcomes of different Haplo-HSCT approaches, one must understand the transplant immunobiology and factors affecting the transplant outcomes. Leukemia remission status at the time of conditioning is a consistent factor affecting the transplant outcomes using any of these platforms. Prospective comparison of these platforms lacks in a homogenous population; however, the evidence is growing, and this review highlights the areas of research gaps.

Treatment Outcomes of Pediatric Acute Myeloid Leukemia in the Yeungnam Region: A Multicenter Retrospective Study of the Study Alliance of Yeungnam Pediatric Hematology-Oncology (SAYPH)

Acute myeloid leukemia (AML) is the second most common pediatric leukemia, with a survival rate of 70%. In this retrospective study, we evaluated the treatment outcomes of pediatric AML among 144 patients diagnosed between 2000 and 2013. After induction, 80.6% of patients achieved complete remission (CR). The 5-year overall survival (OS) and event-free survival (EFS) rates were 58.8 ± 4.2% and 49.8 ± 4.2%, respectively. Based on the response to induction therapy, the 5-year OS was 66.9 ± 5.7% in patients with CR (p < 0.001). Ninety-nine patients with CR after induction therapy were examined, and their 5-year OS and EFS were 66.4 ± 4.9% and 56.3 ± 5.1%, respectively. The 5-year OS rates according to treatment were 59.9 ± 7.4% in the chemotherapy group and 72.3 ± 6.3% in the hematopoietic stem cell transplantation (HSCT) group (p = 0.089). The EFS was 50.1 ± 7.4% in the chemotherapy group and 61.7 ± 6.9% in the HSCT group (p = 0.098). OS and EFS according to cytogenetics were insignificant. Our findings confirmed that the response to induction treatment was important for survival and HSCT had no significant survival benefits compared with those of chemotherapy. Moreover, many early induction deaths under the age of 2 years were observed.

The incidence, risk factors, and outcomes of acute graft-vs-host disease in pediatric T-cell-replete haploidentical hematopoietic stem cell transplantation

The specific description, risk factors, and outcomes of aGVHD in pediatric haplo-HSCT using TCR protocols without PT-Cy have not been well described previously. We evaluated the incidence, risk factors, and outcomes of aGVHD in 350 consecutive pediatric patients receiving TCR haplo-HSCT without PT-Cy according to the Glucksberg and NIH aGVHD classifications between January 2015 and December 2017 at Peking University Institute of Hematology. The cumulative incidences of grade I, II, III, and IV aGVHD were 28%, 29.7%, 8.3%, and 5.1%, respectively. The type of aGVHD onset was classic in 243 patients (97.2%), and persistent/recurrent/late-onset aGVHD was in seven patients (2.8%). None of the considered variables significantly influenced the incidence of grade III-IV aGVHD. The 3-year OS, DFS, cumulative incidence of NRM, and relapse in malignant disease between severe aGVHD (III-IV) group and grade 0-II aGVHD group were 61.5% vs 77.2% (P = .027), 58.6% vs 75.1% (P = .014), 19.8% vs 5.3% (P = .002), and 21.6% vs 19.6% (P = .59), respectively; in non-malignant diseases, the 3-year OS, DFS, and NRM were 81.8% vs 97.4% (P = .05), 81.8% vs 97.4% (P = .05), and 18.2% vs 2.6% (P = .05), respectively. Under the protocol of pediatric TCR haplo-HSCT without PT-Cy, the persistent/recurrent/late-onset aGVHD was rare, and the incidence of severe aGVHD was acceptable and significantly contributed to NRM and lower survival in both malignant disease and non-malignant diseases.

Efficacy of Haploidentical Hematopoietic Stem Cell Transplantation Compared With Chemotherapy as Postremission Treatment of Children With Intermediate-risk Acute Myeloid Leukemia in First Complete Remission

BACKGROUND

The role of haploidentical hematopoietic stem cell transplantation (haplo-HSCT) for children with intermediate-risk acute myeloid leukemia (IR-AML) in first complete remission has been controversial. The present study compared the effect of chemotherapy with unmanipulated haplo-HSCT as treatment of patients with IR-AML in first complete remission (CR1).

PATIENTS AND METHODS

We retrospectively analyzed the outcomes of 80 children with IR-AML and compared the effects of chemotherapy (n = 47) with those of haplo-HSCT (n = 33) as treatment in CR1.

RESULTS

The 3-year overall survival, event-free survival (EFS), and cumulative incidence of relapse (CIR) was 85.4% ± 4.1%, 73.2% ± 5.0%, and 25.4% ± 4.5%, respectively. Compared with the chemotherapy group, the patients in the haplo-HSCT group had a lower CIR (P = .059) and better EFS (P = .108), but roughly equivalent overall survival (P = .841). Multivariate analysis revealed chemotherapy and minimal residual disease (MRD) of ≥ 10^-3 after induction therapy as independent risk factors affecting CIR and EFS. EFS (P = .045) and CIR (P = .045) differed significantly between the 2 treatment groups in patients with MRD of ≥ 10^-3 after induction therapy.

CONCLUSION

Haplo-HSCT might be a feasible option for children with IR-AML in CR1, especially for patients with MRD of ≥ 10^-3 after induction therapy.

Incidence, Risk Factors, and Outcomes of Chronic Graft-versus-Host Disease in Pediatric Patients with Hematologic Malignancies after T Cell-Replete Myeloablative Haploidentical Hematopoietic Stem Cell Transplantation with Antithymocyte Globulin/Granulocyte Colony-Stimulating Factor

The specific description, risk factors, and outcomes of chronic graft-versus-host disease (cGVHD) in pediatric patients with hematologic malignancies after T cell-replete (TCR) myeloablative haploidentical hematopoietic stem cell transplantation (haplo-HSCT) with antithymocyte globulin (ATG)/granulocyte colony-stimulating factor (G-CSF) have not been previously well described. We retrospectively analyzed the incidence, risk factors, and outcomes of cGVHD documented according to the 2014 National Institutes of Health consensus criteria (NIH-CC) in 292 consecutive pediatric patients with hematologic malignancies after TCR myeloablative haplo-HSCT with ATG/G-CSF between January 2015 and December 2017. A total of 170 patients experienced cGVHD. The 3-year cumulative incidence of total cGVHD and mild, moderate, and severe cGVHD was 57.9%, 27.5%, 18.8%, and 11.9%, respectively. Multivariate analysis showed that acute GVHD (aGVHD) grade II-IV (hazard ratio, 1.578; P = .002) was an independent risk factor for cGVHD. Compared to patients without cGVHD, patients with cGVHD demonstrated a lower 3-year relapse (17.6% versus 27.2%; P = .009), a similar 3-year nonrelapse mortality (NRM) (5.9% versus 5.4%; P = .79), and better 3-year disease-free survival (DFS) (77.8% versus 66.9%; P = .007) and overall survival (OS) (81.3% versus 68.6%; P = .001), particularly those with mild or moderate cGVHD; however, no significant impact of severe cGVHD on relapse, NRM, DFS, or OS was seen. In conclusion, the incidence of severe cGVHD in pediatric patients with hematologic malignancies after TCR myeloablative haplo-HSCT with ATG/G-CSF was acceptable. Previous aGVHD grade II-IV was a risk factor for the occurrence of cGVHD. Only mild or moderate cGVHD was associated with a lower risk of relapse, translating into improved DFS and OS in pediatric patients with hematologic malignancies after TCR myeloablative haplo-HSCT with ATG/G-CSF.

Haploidentical- versus identical-sibling transplant for high-risk pediatric AML: A multi-center study

Background

Human leukocyte antigen‐identical sibling donor (ISD)‐hematopoietic stem cell transplantation (SCT) is a potentially curative treatment for high‐risk pediatric acute myeloid leukemia (AML). A haploidentical donor (HID) is readily available to almost all children. Previous studies have demonstrated that patients with HID‐SCT had similar outcomes compared to ISD‐SCT for pediatric and adult AML. However, the role of HID‐SCT in high‐risk pediatric AML is unclear.

Methods

To compare the overall survival of high‐risk AML children who underwent either HID‐SCT or ISD‐SCT, we analyzed 179 cases of high‐risk AML patients under 18 years of age treated with either ISD‐SCT (n = 23) or HID‐SCT (n = 156). Granulocyte colony‐stimulating factor plus anti‐thymocyte globulin‐based regimens were used for HID‐SCT. We also analyzed the subgroup data of AML patients at first complete remission (CR1) before SCT with known cytogenetic risk.

Results

The numbers of adverse cytogenetic risk recipients were 8 (34.8%) and 13 (18.8%) in the ISD‐SCT group and the HID‐SCT group, and the number of patients with disease status beyond CR1 were 6 (26.1%) and 14 (20.3%) in the two groups. The cumulative rates of grades II‐IV acute graft‐versus‐host disease (GVHD) were 13.0% in the ISD‐SCT group and 34.8% in the HID‐SCT group (P = 0.062), with a three‐year cumulative rates of chronic GVHD at 14.1% and 34.9%, respectively (P = 0.091). The relapse rate in the ISD‐SCT group was significantly higher than that in the HID‐SCT group (39.1% vs. 16.4%, P = 0.027); with non‐relapse mortality at 0.0% and 10.6% (P = 0.113), respectively. The three‐year overall survival rates were 73.0% for the ISD‐SCT group and 74.6% for the HID‐SCT group (P = 0.689). In subgroup analysis, the three‐year relapse rate in the ISD‐SCT group was higher than that in the HID‐SCT group (50.0% vs. 9.2%, P = 0.001) and the three‐year DFS in the ISD‐SCT group (50.0%) was lower than that in the HID‐SCT group (81.2%) (P = 0.021).

Conclusions

Unmanipulated HID‐SCT achieved DFS and OS outcomes comparable to those of ISD‐SCT for high‐risk pediatric AML patients with potentially higher rate but manageable GVHD.

Risk factors for chronic graft-versus-host disease after anti-thymocyte globulin-based haploidentical hematopoietic stem cell transplantation in acute myeloid leukemia

Chronic graft-versus-host disease (cGVHD) is a major complication following unmanipulated haploidentical hematopoietic stem cell transplantation (haplo-HSCT). We aimed to identify the risk factors for cGVHD in patients who underwent anti-thymocyte globulin-based haplo-HSCT for acute myeloid leukemia (n = 280). The diagnosis of cGVHD was in accordance with the National Institutes of Health consensus criteria. A total of 169 patients suffered from cGVHD. The patients who had 3 loci mismatched had a higher 8-year incidence of cGVHD (total, 66.0% vs. 53.7%, P = 0.031; moderate to severe, 42.4% vs. 30.1%, P = 0.036) than the patients who had 1 to 2 loci mismatched. The patients who had maternal donors had a higher 8-year incidence of moderate to severe cGVHD (49.2% vs. 32.9%, P = 0.024) compared with the patients who had other donors. The patients who had grades III to IV acute GVHD (aGVHD) had higher 8-year incidence of cGVHD (total, 88.0% vs. 50.4%, P < 0.001; moderate to severe, 68.0% vs. 27.0%, P < 0.001) compared with the patients without aGVHD. In multivariate analysis, grades III to IV aGVHD was the only independent risk factor for cGVHD. Thus, further interventions should be considered in patients with severe aGVHD to prevent cGVHD.

Haploidentical allograft is superior to matched sibling donor allograft in eradicating pre-transplantation minimal residual disease of AML patients as determined by multiparameter flow cytometry: a retrospective and prospective analysis

BACKGROUND

This study compared the effects of pre-transplantation minimal residual disease (pre-MRD) on outcomes in AML patients who underwent human leukocyte antigen-matched sibling donor transplantation (MSDT) or who received unmanipulated haploidentical allografts.

METHODS

A retrospective study (n = 339) and a prospective study (n = 340) were performed. MRD was determined using multiparameter flow cytometry.

RESULTS

Either after retrospective or prospective analysis, patients with negative pre-MRD (pre-MRDneg) had a lower incidence of relapse than those with positive pre-MRD (pre-MRDpos) in MSDT settings (P < 0.001 for all), but relapse was comparable in Haplo-SCT settings for patients with pre-MRDneg versus pre-MRDpos (P = 0.866 and 0.161, respectively). In either the retrospective (n = 65) or the prospective study (n = 76), pre-MRDpos subjects receiving Haplo-SCT experienced a lower incidence of relapse than those who underwent MSDT (P < 0.001 and p = 0.017, respectively). Of the patients with pre-MRDpos in either the total (n = 141) or the subgroup excluding cases which received donor lymphocyte infusion (DLI; n = 105), those who underwent MSDT had a higher incidence of relapse than those receiving haplo-SCT (P < 0.01 for all). Multivariate analysis showed that, for pre-MRDpos cases, haplo-SCT was associated with a low incidence of relapse and with better LFS and OS in either retrospective group, prospective group, combination groups, or subgroup not including cases which received DLI.

CONCLUSIONS

The results indicated that, for pre-MRD-positive AML patients, haplo-SCT was associated with lower incidence of relapse and better survival, suggesting a stronger anti-leukemia effect.