Retrospective cohort study comparing the outcomes of intravenous busulfan vs. total-body irradiation after single cord blood transplantation

Letermovir prophylaxis reduced cytomegalovirus reactivation and resistance post umbilical cord blood transplantation

To explore the impact of letermovir (LET) prophylaxis on cytomegalovirus (CMV) reactivation and resistance in both adult and paediatric umbilical cord blood transplantation (UCBT) patients, we retrospectively compared 43 UCBT patients who received LET as CMV prophylaxis with a historical cohort of 207 UCBT patients without LET usage. LET was administered from Day +1 to Day +100. The 180-day cumulative incidence of CMV reactivation (47.3% vs. 74.4%, p < 0.001) and the proportion of refractory CMV reactivation (15.0% vs. 42.9%, p = 0.016) were significantly lower than those in the control group. However, more frequent late CMV infection (31.0% vs. 4.3%, p = 0.002) and the 180-day cumulative incidence of Epstein-Barr virus (EBV) reactivation (9.3% vs. 3.4%, p = 0.087) were observed in UCBT patients with LET prophylaxis. Meanwhile, older age (>15 years old) and the occurrence of pre-engraftment syndrome were identified as the significant risk factors for CMV reactivation, and in patients at high risk, the incidence of CMV reactivation in the LET group was lower than that in the control group (46.7% vs. 86.5%, p < 0.001), while this decline was less pronounced among patients at low risk (47.8% vs. 62.1%, p = 0.120).

Comparison of busulfan and total body irradiation conditioning on hematopoietic clonal dynamics following lentiviral gene transfer in rhesus macaques

The clonal dynamics following hematopoietic stem progenitor cell (HSPC) transplantation with busulfan conditioning are of great interest to the development of HSPC gene therapies. Compared with total body irradiation (TBI), busulfan is less toxic and more clinically relevant. We used a genetic barcoded HSPC autologous transplantation model to investigate the impact of busulfan conditioning on hematopoietic reconstitution in rhesus macaques. Two animals received lower busulfan dose and demonstrated lower vector marking levels compared with the third animal given a higher busulfan dose, despite similar busulfan pharmacokinetic analysis. We observed uni-lineage clonal engraftment at 1 month post-transplant, replaced by multilineage clones by 2 to 3 months in all animals. The initial multilineage clones in the first two animals were replaced by a second multilineage wave at 9 months; this clonal pattern disappeared at 13 months in the first animal, though was maintained in the second animal. The third animal maintained stable multilineage clones from 3 months to the most recent time point. In addition, busulfan animals exhibit more rapid HSPC clonal mixing across bone marrow sites and less CD16⁺ NK-biased clonal expansion compared with TBI animals. Therefore, busulfan conditioning regimens can variably impact the marrow niche, resulting in differences in clonal patterns with implications for HSPC gene therapies.

Total body irradiation-based versus busulfan-based myeloablative conditioning for single-unit cord blood transplantation in adults

Comparative studies between total body irradiation (TBI)-based and busulfan-based myeloablative conditioning (MAC) regimens for cord blood transplantation (CBT) have been limited. We retrospectively analyzed the results of single-unit CBT in 333 adult patients who received either TBI-based (n = 258) or busulfan-based (n = 75) MAC regimens at our institute. After adjusting for significant variables in the univariate analysis, there were no significant differences in neutrophil recovery (hazard ratio (HR), 0.88; p = .460), grade III-IV acute graft-versus-host disease (GVHD) (HR: 1.40, p = .410), extensive chronic GVHD (HR: 0.73, p = .380), relapse (HR: 0.61, p = .270), non-relapse mortality (HR: 1.38, p = .420), overall survival (HR: 1.18, p = .637), or event-free survival (HR: 1.08, p = .773), although platelet recovery was lower with marginal significance for the busulfan-based regimen (HR: 0.67, p = .068). In subgroup analysis, TBI-based regimens were superior to busulfan-based regimens in terms of survival for acute lymphoblastic leukemia, but not for myeloid malignancies. Further investigation is warranted even for CBT.

Chimeric Antigen Receptor T Cell Therapy followed by Unrelated Cord Blood Transplantation for the Treatment of Relapsed/Refractory B Cell Acute Lymphoblastic Leukemia in Children and Young Adults: Superior Survival but Relatively High Post-Transplantation Relapse

Several studies have indicated that chimeric antigen receptor (CAR) T cell therapy followed by allogeneic hematopoietic stem cell transplantation is beneficial for treating patients with relapsed or refractory (R/R) B cell acute lymphoblastic leukemia (B-ALL). Whether consolidative unrelated cord blood transplantation (UCBT) is suitable in R/R B-ALL after CAR-T therapy remain uncertain. We aimed to assess the efficacy and safety of CAR-T therapy before UCBT in children and young adults with R/R B-ALL. We retrospectively analyzed 43 patients aged <18 years with R/R B-ALL who underwent single-unit UCBT at the First Affiliated Hospital of the University of Science and Technology of China between February 2012 and November 2020. Among them, 21 patients achieved complete remission (CR) following CAR-T therapy before UCBT (the CAR-T group), and the remaining 22 patients remained in nonremission (NR) without prior CAR-T therapy before UCBT (the NR group). The clinical outcomes in the 2 groups were analyzed. The median time from CAR-T therapy to UCBT was 62 days (range, 42 to 185 days). There were no significant between-group differences in the incidences of grade II-IV acute graft-versus-host disease (GVHD), grade III-IV acute GVHD, and 2-year extensive chronic GVHD. Compared with the NR group, the CAR-T group had a lower 2-year cumulative incidence of transplantation-related mortality and higher probabilities of 2-year overall survival, leukemia-free survival, and GVHD-free relapse-free survival (P = .037, .005, .028, and .017, respectively). However, the 2-year cumulative incidence of relapse (CIR) was comparably high in the 2 groups (26.7% in the CAR-T group and 38.3% in the NR group; P = .41). In the CAR-T group, patients who were minimal residual disease (MRD)-positive before UCBT had a higher CIR compared with those who were MRD-negative before UCBT (66.7% versus 19.2%; P = .006). CAR-T therapy followed by UCBT produces superior survival in R/R B-ALL, but treated patients still have a high post-transplantation relapse rate.

Poor survival and prediction of prolonged isolated thrombocytopenia post umbilical cord blood transplantation in patients with hematological malignancies

Prolonged isolated thrombocytopenia (PIT) is a common complication after umbilical cord blood transplantation (UCBT). However, data on PIT prediction and impacts on transplantation outcomes for UCBT patients are rare. We retrospectively analyzed 244 patients with hematological malignancies who received single-unit UCBT at the First Affiliated Hospital of USTC between August 2018 and December 2019. Among them, PIT occurred in 49 recipients, with a crude incidence of 20.1%. In the PIT patients, the 2-year cumulative incidence of transplant-related mortality (TRM) was significantly higher, and the probabilities of 2-year overall survival, leukemia-free survival and graft-versus-host disease (GVHD)-free relapse-free survival were significantly poorer (57.1% vs. 88.6%; 53.1% vs. 81.9%; 22.4% vs. 59.8%; p < 0.001), without remarkable increases in the cumulative incidence of relapse or chronic GVHD. Importantly, the multivariate analysis revealed that lower high-resolution HLA compatibility (≤6/10), lower infused CD34⁺ cell count (≤1.78 × 10⁵ /kg), grade II-IV acute GVHD preplatelet engraftment, a lower pretransplantation platelet count (≤100 × 10⁹ /L), and a longer neutrophil engraftment time (≥17 days) were independent risk factors for PIT after UCBT. These results demonstrate that PIT is common after UCBT, predicting inferior survival and the need for more monitoring during the early phase.

[Unrelated cord blood stem cell transplantation for high-risk/refractory childhood acute myeloid leukemia: a clinical analysis of 160 cases]

Objective: To retrospectively analyze the clinical outcomes of single unrelated cord blood transplantation (UCBT) in children with high risk and refractory acute myeloid leukemia (AML) . Methods: Between June 2008 and December 2018, a total of 160 consecutive pediatric patients with AML received single UCBT (excluding acute promyelocytic leukemia) . Myeloablative conditioning (MAC) regimen were applied. All patients received a combination of cyclosporine A (CsA) and mycophenolate mofetil (MMF) for the prophylaxis of graft -versus- host disease (GVHD) . Results: The cumulative incidence of neutrophil cells engraftment at day +42 and platelet recovery at day +120 was 95.0% (95% CI 90.0%-97.5%) at a median of 16 days after transplantation (range, 11-38 days) and 85.5% (95%CI 83.3%-93.4%) with a median time to recovery of 35 days (range, 13-158) , respectively. Incidence of grades Ⅱ-Ⅳ and Ⅲ-Ⅳ acute GVHD and chronic GVHD were 37.3% (95%CI 29.3%-45.2%) , 27.3% (95%CI 20.0%-35.0%) and 22.4% (95%CI 15.5%-28.7%) , respectively. The transplant-related mortality (TRM) at 360 day was 13.1% (95%CI 8.4%-18.9%) . The 5-year cumulative incidence of relapse was 13.8% (95%CI 8.5%-20.3%) . The 5-year disease-free survival (DFS) and overall survival (OS) were 71.7% (95%CI 62.7%-77.8%) and 72.2% (95%CI 64.1%-78.7%) , respectively. The 5-year GVHD and relapse free survival (GRFS) was 56.1% (95%CI 46.1%-64.9%) . The 5-year cumulative recurrence rates of CR1, CR2, and NR groups were 5.3%, 19.9%, and 30.9% (P=0.001) , and the 5-year OS rates were 79.9% (95%CI 70.3%-86.7%) , 71.1% (95%CI 50.4%-84.4%) and 52.9% (95%CI 33.0%-69.3%) (χ(2)=7.552, P=0.020) , respectively. Conclusions: For pediatric patients with high risk and refractory AML, UCBT is a safe and effective treatment option, and it is favorable to improve the survival rate in CR1 stage.

Umbilical cord blood transplantation can overcome the poor prognosis of KMT2A-MLLT3 acute myeloid leukemia and can lead to good GVHD-free/relapse-free survival

This is a retrospective study comparing the effectiveness of umbilical cord blood transplantation (UCBT) and chemotherapy for patients in the first complete remission period for acute myeloid leukemia with KMT2A-MLLT3 rearrangements. A total of 22 patients were included, all of whom achieved first complete remission (CR1) through 1–2 rounds of induction chemotherapy, excluding patients with an early relapse. Twelve patients were treated with UCBT, and 10 patients were treated with chemotherapy after 2 to 4 courses of consolidation therapy. The 3-year overall survival (OS) of the UCBT group was 71.3% (95% CI, 34.4–89.8%), and that of the chemotherapy group was 10% (95% CI, 5.89–37.3%). The OS of the UCBT group was significantly higher than that of the chemotherapy group (P = 0.003). The disease-free survival (DFS) of the UCBT group was 60.8% (95% CI, 25.0–83.6%), which was significantly higher than the 10% (95% CI, 5.72–35.8%) of the chemotherapy group (P = 0.003). The relapse rate of the UCBT group was 23.6% (95% CI, 0–46.8%), and that of the chemotherapy group was 85.4% (95% CI, 35.8–98.4%), which was significantly higher than that of the UCBT group (P < 0.001). The non-relapse mortality (NRM) rate in the UCBT group was 19.8% (95% CI, 0–41.3%), and that in the chemotherapy group was 0.0%. The NRM rate in the UCBT group was higher than that in the chemotherapy group, but there was no significant difference between the two groups (P = 0.272). Two patients in the UCBT group relapsed, two died of acute and chronic GVHD, and one patient developed chronic GVHD 140 days after UCBT and is still alive, so the GVHD-free/relapse-free survival (GRFS) was 50% (95% CI, 17.2–76.1%). AML patients with KMT2A-MLLT3 rearrangements who receive chemotherapy as their consolidation therapy after CR1 have a very poor prognosis. UCBT can overcome the poor prognosis and significantly improve survival, and the GRFS for these patients is very good. We suggest that UCBT is a better choice than chemotherapy for KMT2A-MLLT3 patients.