A new intensive conditioning regimen for allogeneic hematopoietic stem cell transplantation in patients with refractory or relapsed acute myeloid leukemia

Impact of cladribine, cytarabine, and G-CSF (CLAG) as a bridging therapy prior to allogeneic hematopoietic stem cell transplantation in relapsed or refractory acute myeloid leukemia

The combination of cladribine, cytarabine, and G-CSF (CLAG) has exhibited robust synergistic anti-leukemia activity as an induction therapy (IT) in acute myeloid leukemia (AML). However, the impact of CLAG as a bridging therapy (BT) administered between IT and allogeneic hematopoietic stem cell transplantation (allo-HSCT) for patients with relapsed or refractory (R/R) AML remains uncertain. In this retrospective study, we examined the efficacy of CLAG as a transitional strategy prior to allo-HSCT in R/R AML. We included 234 patients with R/R AML who received the modified busulfan plus cyclophosphamide conditioning regimen for allo-HSCT in our center during the past 6 years, performed a propensity-score matching analysis, partitioned them into four distinct cohorts, and further integrated them into the CLAG group and non-CLAG group based on response to IT and utilization of CLAG. Our cohorts encompassed 12 patients in Cohort A (modified composite complete remission (mCRc) after IT, CLAG), 31 in Cohort B (mCRc after IT, non-CLAG), 35 in Cohort C (non-complete remission (non-CR) after IT, CLAG), and 80 in Cohort D (non-CR after IT, non-CLAG). Intriguingly, among patients with non-CR status, the administration of CLAG correlated with a notably statistically diminished risk of relapse and improved survival at 2-year follow-up (Cohort C vs. Cohort D). Employing CLAG as a BT prior to allo-HSCT demonstrates substantial effectiveness, a relative degree of safety, and manageable toxicity in selected R/R AML cases.

CLAG combined with total body irradiation as intensive conditioning chemotherapy prior to allogeneic hematopoietic stem cell transplantation in patients with refractory or relapsed acute myeloid leukemia

Refractory or relapsed acute myeloid leukemia (R/R AML) remains the major challenge of AML treatment. Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is the only valid option to achieve cure, but the prognosis is still dismal. We conducted a retrospective analysis for the feasibility of CLAG regimens (cladribine, cytarabine, and granulocyte colony-stimulating factor) combined with total body irradiation (TBI) as new intensive conditioning chemotherapy prior to HSCT in R/R AML. A total of 70 patients, including 21 primary refractory and 49 relapsed AML, were analyzed. Forty-nine (70%) patients had extramedullary diseases, and 54 (77%) patients received haploidentical transplantation. Except for one who died before white blood cell engraftment, all of the 69 evaluable patients achieved measurable residual disease (MRD) negative complete remission. The 3-year overall survival (OS) and relapse-free survival (RFS) rates were 46.0% (95% confidence interval [CI], 33.5-57.7%) and 38.5% (95%CI, 26.8-50.0%). The 1-year cumulative incidences of relapse and non-relapse mortality (NRM) were 38.6% (95%CI, 27.3-49.3%) and 11.6% (95%CI: 5.4-20.3%), respectively. The presence of chronic graft-versus-host disease (cGVHD) showed a trend to be associated with a lower risk of relapse (P = 0.054) and extramedullary diseases with a higher risk of NRM (P = 0.074). Multivariate analyses identified low leukemia burden pre-HSCT (defined as bone marrow blasts ≤ 50%) and cGVHD as independent factors associated with favorable OS and RFS. In conclusion, intensive conditioning with CLAG regimens plus TBI may be an effective and well-tolerated choice for R/R AML patients undergoing allo-HSCT.

Cladribine- and decitabine-containing conditioning regimen has a low post-transplant relapse rate in patients with relapsed or refractory acute myeloid leukemia and high-risk myelodysplastic syndrome

To reduce the risk of relapse after allogeneic hematopoietic stem cell transplantation (allo-HSCT), there have been continuing efforts to optimize the conditioning regimens. Our study aimed to analyze the risk factors associated with the relapse of relapsed/refractory (R/R), high-risk acute myeloid leukemia (AML) and high-risk myelodysplastic syndrome (MDS) post-transplant and the efficacy of a new conditioning regimen involving decitabine and cladribine. Clinical data of 125 patients with R/R AML, high-risk AML and high-risk MDS who underwent allo-HSCT were collected. In addition, 35 patients with R/R AML, high-risk AML and high-risk MDS received treatment with a new conditioning regimen including decitabine and cladribine. Cox regression analysis was used to identify risk factors associated with OS, RFS and relapse. Among 125 patients who underwent allo-HSCT, CR before allo-HSCT and matched sibling donors were independent protective factors for OS. DNMT3A abnormality was an independent risk factor for both relapse and RFS. Among 35 patients who received a new conditioning regimen containing decitabine and cladribine, only six patients relapsed and 1-year cumulative incidence of relapse was 11.7%. Moreover, this new regimen showed efficient MRD clearance early after allo-HSCT. The combined decitabine- and cladribine-based conditioning regimen showed a low relapse rate and a high survival without an increased incidence of GVHD or adverse effects and thus has potential for use in allo-HSCT for R/R AML, high-risk AML and high-risk MDS.

Refractory hepatosplenic T-cell lymphoma was successfully treated with salvage allogeneic hematopoietic stem cell transplantation combined with enhanced myeloablative preconditioning

This study aims to evaluate the clinical benefit of salvage allogeneic hematopoietic stem cell transplantation (allo-HSCT) in combination with enhanced myeloablative preconditioning in the treatment of refractory liver and spleen T-cell lymphomas. A retrospective analysis was performed on three patients (with refractory liver and spleen T-cell lymphomas) who have been treated with salvage allo-HSCT combined with enhanced myeloablative preconditioning. One of three patients had a liver biopsy; the other two underwent bone marrow analysis using morphology, immunology, cytogenetics, and molecular biology. All three patients were resistant to chemotherapy and with a high tumor load, so a new total body irradiation/splenic region irradiation/GEM/CLAG/ATG preconditioning regimen was conducted and followed with salvage HSCT. Two patients received haploidentical-donor hematopoietic stem cell transplants, and one received an unrelated full-donor hematopoietic stem cell transplant. The three patients survived disease-free until May 2021. Clinically, hepatosplenic T-cell lymphoma (HSTCL) is rare, with a poor prognosis and chemotherapy response. Based on the present study's encouraging clinical results, salvage allo-HSCT in conjunction with an enhanced myeloablative preconditioning regiment may be an effective and safe treatment for HSTCL.

Decitabine-Intensified Modified Busulfan/Cyclophosphamide Conditioning Regimen Improves Survival in Acute Myeloid Leukemia Patients Undergoing Related Donor Hematopoietic Stem Cell Transplantation: A Propensity Score Matched Analysis

To identify the benefit of decitabine (Dec)-intensified myeloablative conditioning on the outcomes of patients with acute myeloid leukemia (AML) after related donor hematopoietic stem cell transplantation (HSCT), we performed a retrospective matched-pair study from a pool of 156 patients to evaluate Dec [20 mg/m²/day intravenously (i.v.) on days -11 to -7]-intensified modified busulfan/cyclophosphamide (mBuCy) conditioning regimen vs. mBuCy regimen in 92 AML patients, with 46 patients in each cohort. The cumulative incidence of grade II-IV acute graft-versus-host disease (aGVHD) was lower in the Dec group (15.2% ± 0.3% vs. 32.6% ± 0.5%, P = 0.033). Compared with mBuCy group (15.5% ± 0.3%), a significantly higher proportion of limited chronic GVHD (cGVHD) in Dec group (35% ± 0.6%) was observed (P = 0.025). Dec-intensified mBuCy conditioning was associated with better 2-year overall survival (OS) and GVHD-free relapse-free survival (GRFS) (81% ± 6.2% vs. 59.4% ± 7.5%, P = 0.03; 58.7% ± 8.1% vs. 40.9% ± 7.3%, P = 0.042; respectively). Our results also elucidated that the Dec group had better 2-year OS and lower 2-year cumulative incidence of relapse (CIR) in patients acquiring haploidentical HSCT than that of the mBuCy group (84.8% ± 7.1% vs. 58.2% ± 10.3%, P = 0.047; 17.9% ± 0.8% vs. 40.0% ± 1.0%, P = 0.036; respectively), which did not increase the treatment-related mortality and regimen-associated toxicities. Dec-intensified myeloablative regimen and high-risk stratification were the variables associated with OS, leukemia-free survival (LFS), and GRFS in multivariate analysis. In high-risk patients, no differences were found in CIR, OS, LFS, and GRFS between the two groups. These data indicated that Dec-intensified mBuCy conditioning regimen was associated with better survival than mBuCy regimen in AML patients, especially in patients undergoing haploidentical HSCT.

MRD abnormal expression predict poor outcomes for refractory or relapsed acute myeloid leukemia after allogeneic hematopoietic stem cell transplantation

We retrospectively analyzed data from 197 patients with refractory or relapsed acute myeloid leukemia (r/rAML) who underwent allo‐HCT between January 2013 and February 2020 in our center (patients with promyelocytic leukemia were excluded). Of all patients, 86 achieved a complete morphological remission (CR) before transplant, while 111 failed to do so (NR). In the CR group, 32 patients displayed minimal residual disease (MRD‐positive). According to their immunophenotype pre‐HCT, we divided the MRD‐positive group and NR group into three subgroups: MRD 0+ group (without any antigen abnormal expression of CD7+, CD56+, CD38−, or HLA‐DR−) 28 patients, MRD 1+ group (with one abnormal antigen expression of CD7+, CD56+, CD38−, or HLA‐DR−) 63 patients, MRD 2+ group (with two or more abnormal antigens expression of CD7+, CD56+, CD38‐, or HLA‐DR‐) 52 patients. 3‐year estimates of disease‐free survival (DFS) for MRD 0+, MRD 1+ and MRD 2+ patients were 59.5 ± 9.5%, 29.9 ± 6.1%, and 9.4 ± 5.1%, and 3‐year estimates of overall survival (OS) were 59.5 ± 9.5%, 34.5 ± 6.3%, and 14.5 ± 10.8%, respectively. Multivariate analysis adjusted for genetic risk, blast cell level, secondary disease, age, sex, and donor relationship pre‐HCT, the hazard ratios of abnormal expression of CD7+, CD56+, HLA‐DR−, and CD38^‐ were 6.69 (range 2.08–21.52; p = 0.001) for DFS, 2.24 (range 1.21–4.14; p = 0.010) for OS, and 7.18 (range 2.23–23.10; p = 0.001) for relapse compared with CD7−, CD56−, HLA‐DR+, and CD38+ patients. Our finding suggested that abnormal expression of CD7+, CD56+, HLA‐DR−, and CD38− is associated with poor outcomes, and the more number of abnormal antigens expression predict worse outcomes.

The use of venetoclax-based salvage therapy for post-hematopoietic cell transplantation relapse of acute myeloid leukemia

For patients with high risk myeloid disease, allogeneic hematopoietic cell transplantation (HCT) is the only potentially curative therapy. Unfortunately, many of these patients relapse after HCT and have a limited survival. The recent approval of venetoclax, an orally bioavailable BCL-2 inhibitor, resulted in significant responses in treatment naïve acute myeloid leukemia (AML), and off-label use in the relapsed/refractory setting is increasing. We report the outcomes of 21 patients who underwent allogeneic HCT for myeloid disease, relapsed with AML, and were treated with venetoclax. Several patients had poor risk features including antecedent hematologic malignancy (6/21), complex karyotype (6/21), and TP53 mutations (5/21). The median age was 64.5 years and time from HCT to relapse was 5.7 months (range: 0.9 to 44.9 months). Of the 19 patients who were assessed for response, there were meaningful treatment responses seen in eight patients: five CR, three CRi, zero PR, for an ORR of 42.1%. Treatment effect was seen in six additional patients, including four in the morphologic leukemia-free state. Nine patients maintained their response for ≥3 months and eight were receiving therapy at data cut. Post-HCT AML relapse has an exceedingly poor outcome, and venetoclax-based therapy is a potent therapy option that should be studied prospectively in this setting.

Emerging agents and regimens for treatment of relapsed and refractory acute myeloid leukemia

Relapsed and refractory acute myeloid leukemia (R/R AML) has complicated pathogenesis. Its treatment is complicated, and the prognosis is poor. So far, there is no consensus on what is the optimal treatment strategy. With the deepening of research, new chemotherapy regimens, new small molecule inhibitors, and immunotherapy have been increasingly applied to clinical trials, providing more possibilities for the treatment of R/R AML. The most effective treatment for patients who achieve complete remission after recurrence is still sequential conditioning therapy followed by allogeneic hematopoietic cell transplantation. Finding the best combination of treatments is still an important goal for the future.