Bridging the gap: understanding contemporary autopsies in acute leukemia by comparing ante-mortem and post-mortem profiles.

This study investigates acute myeloid leukemia/lymphoblastic leukemia (AML/ALL) through a 14-year analysis (2009-2022) of 46 autopsied cases (age >12 years). B-ALL was the dominant subtype (34.8%). Liver and spleen were the common sites of active leukemia (63% cases). Symptoms like dyspnea and altered sensorium associated significantly with heart (p = .031) and brain leukostasis (p = .006). Measurable residual disease (MRD) negativity correlated with disease-free status outside the bone marrow, while MRD-positive cases displayed leukemic infiltrates. Infections were identified in 23 autopsied cases, notably linked to post-induction and post-transplant fatalities. Surprisingly, 18 of these 23 cases had unexpected infections mainly fungal (13 cases) with Aspergillus species as the most common. Diagnostic discrepancies were identified in 48% of cases. Malignant infiltration (46%) and infections (25%) were the leading causes of death. This research sheds light on leukemia in extra-medullary tissues, uncovers novel clinical-pathological associations, and highlights overlooked therapy side effects, offering insights for future case management.

Mixed-phenotype (B-lymphocytic/myeloid) acute leukemia with ETV6-ABL1 expression.

Objectives: Mixed-phenotype acute leukemia (MPAL) is rare in the clinic, accounting for approximately 2%-5% of acute leukemia cases. Methods: In this study the cohort included 126 patients, of which 125 cases were from re-examined published data and current patients from Shenzhen Longhua District Central Hospital, carrying an ETV6-ABL1 rearrangement from April 15, 2020 to December 19, 2020. The ETS variant transcription factor 6-Abelson proto-oncogene 1 (ETV6-ABL1) fusion gene is mainly seen in malignant hematological diseases such as acute myeloid leukemia (AML), acute lymphocytic leukemia (ALL), myeloproliferative neoplasms (MPNs). Positivity of both MPAL and ETV6-ABL1 suggest a poor prognosis. This is the first report of B lymphocytic/myeloid mixed-phenotype acute leukemia with ETV6-ABL1 fusion gene positivity. Complete remission was achieved with chemotherapy for lymphoid and myeloid leukemia and targeted therapy with tyrosine kinase inhibitors (TKIs). Results: The level of ETV6-ABL1/ABL decreased from 23.056% to 11.165%. After consolidation chemotherapy, the patient underwent allogeneic hematopoietic stem cell transplantation but died due to intestinal rejection. There are 126 cases of ETV6-ABL1 fusion gene transcript expression in numerous hematologic malignancies reported to date, including 48 cases of ALL, 12 of AML, and 65 of MPN. Eosinophilia is a common characteristic, especially in MPN patients. Conclusion: Survival analysis suggests that the survival time of ALL and MPN patients receiving TKI treatment is better than that of patients not receiving this treatment. Dasatinib or nilotinib, especially the former, is more effective than imatinib for MPN.

[Clinical Characteristics and Prognosis of Patients with Acute Leukemia Complicated with Mucormycosis after Chemotherapy].

OBJECTIVE: To analyze the characteristics and prognosis of patients with mucormycosis after chemotherapy for acute leukemia, and to strengthen understanding of the disease. METHODS: 7 cases of acute leukemia (AL) patients diagnosed with mucormycosis by metagenomic next generation sequencing (mNGS) after chemotherapy at the First Affiliated Hospital of Bengbu Medical College from October 2021 to June 2022 were collected, and their clinical data, including clinical characteristics, diagnosis, treatment, and prognosis, were retrospectively analyzed. RESULTS: Among the 7 patients with AL complicated with mucormycosis, there were 3 males and 4 females, with a median age of 52(20-59) years. There were 6 cases of acute myeloid leukemia (AML) and 1 case of acute lymphocytic leukemia (ALL). Extrapulmonary involvement in 4 cases, including 1 case suspected of central nervous system involvement. The median time for the occurrence of mucor infection was 16(6-69) days after chemotherapy and 19(14-154) days after agranulocytosis. The main clinical manifestations of mucormycosis were fever (7/7), cough (3/7), chest pain (3/7) and dyspnea (1/7). The most common chest CT imaging findings were nodules, patchy or mass consolidation (6/7). All patients were treated with posaconazole or voriconazole prophylaxis during neutropenia phase. 5 patients died within 8 months, and the median time from diagnosis to death was 1 month. CONCLUSION: Although prophylactic antifungal therapy is adopted, patients with acute leukemia still have a risk of mucor infection during the neutropenia phase. Fever is the main manifestation in the early stage of mucor infection. The use of intravenous antifungal drugs alone is ineffective and there is a high mortality rate in acute leukemia patients with mucormycosis.

Assessing the impact of COVID-19 on acute leukemia patients: a comparative analysis of hematological and biochemical parameters.

BACKGROUND: The impact of COVID-19 infection on the blood system remains to be investigated, especially with those encountering hematological malignancies. It was found that a high proportion of cancer patients are at an elevated risk of encountering COVID-19 infection. Leukemic patients are often suppressed and immunocompromised, which would impact the pathology following COVID-19 infection. Therefore, this research aims to bring valuable insight into the mechanism by which COVID-19 infection influences the hematological and biochemical parameters of patients with acute leukemia. METHODS: This retrospective investigation uses repeated measures to examine changes in hematological and biochemical parameters among patients with acute leukemia before and after COVID-19 infection at a major Saudi tertiary center. The investigation was conducted at the Ministry of National Guard-Health Affairs in Riyadh, Saudi Arabia, on 24 acute leukemia patients with COVID-19 between April 2020 and July 2023. The impact of COVID-19 on clinical parameters, comorbidities, and laboratory values was evaluated using data obtained from the electronic health records at four designated time intervals. The relative importance of comorbidities, testing preferences, and significant predictors of survival was ascertained. RESULTS: The majority of leukemic COVID-19-infected patients, primarily detected through PCR tests, were diagnosed with acute lymphoblastic leukemia (70.8%). The hematological and biochemical parameters exhibited stability, except for a brief increase in ALT and a sustained rise in AST. These changes were not statistically significant, and parameters remained normal at all time points. Additionally, an increase in monocyte count was shown at time point-3, as well as platelet counts at time point 2. CONCLUSION: While this study did not detect statistically significant effects of COVID-19 on biochemical and hematological parameters in acute leukemia patients, further investigation is needed to fully understand the potential adverse reactions and modifications following COVID-19 infection.

Donor's age influences outcome in haploidentical hematopoietic stem cell transplantation with post-transplant cyclophosphamide - a single center experience.

Haploidentical stem cell transplantation (haplo-SCT) using post-transplantation cyclophosphamide (post-Cy) is considered a reasonable therapeutic option for patients who lack matched donor or who urgently need transplant procedure due to high risk disease. We analyzed the results of haplo-SCT performed in years 2018-2023. Eighty one patients (46 males) at median age of 52 years underwent haplo-SCT using peripheral blood as a stem cell source in most cases. Indications included hematological malignancies (acute leukemias in 88% of cases). In 25 cases (31%) transplantation was performed in relapsed/refractory disease. Majority of patients (61%) presented with very high and high disease risk index (DRI). Conditioning regimens were as follows: nonmyeloablative - 46 cases (57%), myeloablative - in 18 (22%) and reduced intensity - 17(20%). 90% of patients engrafted. All patients received unified immunosuppressive treatment (post-Cy/TAC/MMF). Median follow-up time was 12 months The cumulative incidence of acute and chronic GVHD was 37.5% and 37.6%, respectively. Estimated 2-year overall survival (OS) was 43.1% and donor's age was the only factor influencing survival. The 2-year progression-free survival (PFS) was 42.5%, whereas relapse incidence (RI) - 35%. The cumulative incidence of non-relapse mortality (NRM) was 44% and was mostly due to infections. Haplo-SCT is a feasible treatment option for hematological patients. Younger donor improves post-transplant survival. Strategies to reduce infection-related mortality and relapse rate remain a challenge.

Molecular characterization of V(D)J rearrangements in immature acute leukemias.

Early T-cell Precursor Acute Lymphoblastic Leukemia (ETP-ALL), T-Lymphoid/Myeloid Mixed Phenotype Acute Leukemia (T/M-MPAL), and Acute Myeloid Leukemia with minimal differentiation (AML-M0) are immature acute leukemias (AL) that present overlapping T-cell lymphoid and myeloid features at different degrees, with impact to disease classification. An interesting strategy to assess lymphoid lineage commitment and maturation is the analysis of V(D)J gene segment recombination, which can be applied to investigate leukemic cells in immature AL. Herein, we revisited 19 ETP-ALL, 8 T/M-MPAL, and 12 AML-M0 pediatric patients to characterize V(D)J rearrangement (V(D)J-r) profiles associated with other somatic alterations. V(D)J-r were identified in 74 %, 25 %, and 25 % of ETP-ALL, T/M-MPAL, and AML-M0, respectively. Forty-six percent of ETP-ALL harbored ≥ 3 V(D)J-r, while there was no more than one V(D)J-r per patient in AML-M0 and T/M-MPAL. TCRD was the most rearranged locus in ETPALL, but it was not rearranged in other AL. In ETP-ALL, N/KRAS mutations were associated with absence of V(D)J-r, while NF1 deletion was most frequent in patients with ≥ 3 V(D)J-r. Relapse and death occurred mainly in patients harboring one or no rearranged locus. Molecular characterization of V(D)J-r in our cohort indicates a distinct profile of ETP-ALL, compared to T/M-MPAL and AML-M0. Our findings also suggest that the clinical outcome of ETP-ALL patients may be affected by blast cell maturity, inferred from the number of rearranged TCR loci.

Single-cell transcriptomic analysis of the immune microenvironment in pediatric acute leukemia.

Relapse and treatment resistance pose significant challenges in the management of pediatric B cell acute lymphoblastic leukemia (B-ALL) and acute myeloid leukemia (AML). The efficacy of immunotherapy in leukemia remains limited due to factors such as the immunosuppressive tumor microenvironment (TME) and lack of suitable immunotherapeutic targets. Thus, an in-depth characterization of the TME in pediatric leukemia is warranted to improve the efficacy of immunotherapy. Here, we used single-cell RNA sequencing (scRNA-seq) to characterize the TME of pediatric B-ALL and AML, focusing specifically on bone-marrow-derived T cells. Moreover, we investigated the transcriptome changes during the initiation, remission, and relapse stages of pediatric AML. Our findings revealed that specific functional expression programs correlated with fluctuations in various T cell subsets, which may be associated with AML progression and relapse. Furthermore, our analysis of cellular communication networks led to the identification of VISTA, CD244, and TIM3 as potential immunotherapeutic targets in pediatric AML. Finally, we detected elevated proportions of γδ T cells and associated functional genes in samples from pediatric patients diagnosed with B-ALL and AML, which could inform the development of novel therapeutic approaches, potentially focusing on γδ T cells.

Acute leukemia with KMT2A rearrangement: A master of disguise.

Mixed-phenotype acute leukemia (MPAL) is a rare form of leukemia with ambiguous lineage, and there are challenges in accurately diagnosing this entity according to formal criteria. Here we report a case which was initially diagnosed as "AML" based on atypical peripheral blood flow cytometry that was subsequently determined to be B-ALL with KMT2A rearrangement based on marrow results. Although KMT2A rearrangements represent a defining genetic abnormality for acute leukemia of ambiguous lineage, this case did not meet the criteria for MPAL based on WHO 2022 criteria. This case highlights the diagnostic challenges of MPAL and the potential limitations of the current classification. We discuss the most appropriate workup and management of these patients and identify areas for future study.

Patient Preferences for Treatment in Relapsed/Refractory Acute Leukemia in the United Kingdom: A Discrete Choice Experiment.

Background: Acute leukemia is a cancer of the white blood cells which progresses rapidly and aggressively. There are two types: acute lymphoblastic leukemia (ALL) and acute myeloid leukemia (AML). The latter has a rare subtype: acute promyelocytic leukemia (APL). For some patients, following first-line treatment, remission is not achieved ("refractory disease"), and for others the leukemia returns after achieving remission ("relapse"). For these individuals, outcomes are typically poor. It is, therefore, important to understand patients' treatment priorities in this context. Methods: Building upon formative qualitative research, an online survey containing a discrete choice experiment (DCE) was designed to explore patients' treatment preferences in the relapsed/refractory setting. The DCE attributes were mode of administration; quality of life during treatment; chance of response; duration of response; and quality of life during response. Each respondent completed twelve scenarios containing two hypothetical treatments. Participants were eligible if they lived in the United Kingdom and had a diagnosis of acute leukemia. The data were analysed using a latent class model. Results: A total of 95 patients completed the survey. The latent class analysis identified two classes. For both, chance of response was the most important attribute. For class 1, every attribute was important, whereas for class 2, the only important attributes were quality of life (during treatment and response) and chance of response. A greater proportion of respondents would fall into class 1 overall, and those with ALL or APL and those more recently diagnosed were more likely to be in class 2. Conclusion: Our results indicate that patients are strongly concerned about the chance of response, as well as quality of life (to a lesser extent), when faced with different treatment options in the relapsed/refractory setting. However, there is significant preference heterogeneity within the patient population, and other treatment characteristics also matter to many.

Management of acute appendicitis in pediatric patients with acute leukemia: Insights from a single-center study.

Acute appendicitis (AA) in pediatric patients with acute leukemia mandates prompt treatment. Diagnosis presents challenges, relying on clinical and radiological assessments, often leading to treatment delays that may disrupt leukemia management. Our study on 14 such cases underscores the pivotal role of swift intervention. While conservative AA treatment may pose no risk to healthy children, our findings mandate the performance of laparoscopic appendectomy within 24 hours of diagnosis. This strategy yielded successful surgical outcomes while ensuring uninterrupted leukemia care. Our experience contributes important insights to the limited understanding of navigating this complex clinical scenario.

PICALM::MLLT10 may indicate a new subgroup of acute leukemias with miscellaneous immunophenotype and poor initial treatment response but showing sensitivity to venetoclax.

The PICALM::MLLT10 fusion gene is a rare but recurrent event in acute leukemia (AL) associated with poor prognosis. It is still confused whether PICALM::MLLT10 can solely correspond to acute myeloid leukemia (AML) or acute lymphoblastic leukemia (ALL) or acute leukemias of ambiguous lineage (ALAL). Here, we reported a series of PICALM::MLLT10 positive AL patients with miscellaneous immunophenotype including T-ALL, ALAL, AML, and B-ALL, complex karyotype, half of extramedullary disease (EMD), frequently concomitant PHF6 mutation, and poor initial treatment response to standard chemotherapy aiming to different immunophenotype, but showing sensitivity to combining chemotherapy especially integrated with venetoclax, suggesting this fusion gene may indicate a new subgroup of AL. Eighteen PICALM::MLLT10 positive patients of 533 AL patients (18/533, 3.4%) were identified by RNA sequencing in our center. We found PICALM::MLLT10 positive AL showing miscellaneous immunophenotype, higher expression of leukemic stemness genes and lower expression of biomarkers of venetoclax resistance, more extramedullary involvement, and especially poor response to conventional induction chemotherapy, but may benefit from venetoclax as well as low-dose Ara-C, granulocyte colony-stimulating factor (G-CSF), and anthracyclines combination chemotherapy. Sequential hematopoietic stem cell transplantation (HSCT) after chemotherapy combined with venetoclax may further improve long-term survival in AL patients with complete remission (CR) even measurable residual disease (MRD) positive.

Applications of 18F-Fluorodesoxyglucose PET Imaging in Leukemia.

The main finding that 18F-FDG PET imaging can reveal in patients with leukemias is the presence of bone marrow (BM) infiltration in both acute or chronic forms. This ability can influence and guide the use of BM biopsy but also assess to therapy response. Additionally 18F-FDG PET imaging has been reported as particularly useful for the diagnosis of leukemias in patients with non specific symptoms. In the case of acute leukemias it revealed also a role for the evaluation of extramedullary forms while in the case of chronic forms a role for the assessment of Richter transformation has been reported.

Atypical BCR-ABL1 transcript in mixed phenotype acute leukemia with bone marrow necrosis.

Mixed phenotype acute leukemia (MPAL) is a type of acute leukemia in which encompasses mixed features of myeloid, T-lymphoid, and/or B-lymphoid differentiation. Philadelphia chromosome-positive (Ph+) MPAL is a rare subgroup with a poor prognosis and accounts for ＜1% of adult acute leukemia. Until now, there is still no consensus on how to best treat Ph+ MPAL. Here, we report a 62-year-old male with Ph+ (atypical e13a2 BCR-ABL1 fusion protein) MPAL. This patient presented with recurrent and intense bone pain due to bone marrow necrosis (BMN). Besides, he did not achieve a complete remission for the first two chemotherapies, until he received flumatinib combined with hyper-CVAD (B) (a dose-intensive regimen include methotrexate and cytarabine). To our knowledge, this is the first report to describe the coexistence of BMN and atypical e13a2 BCR-ABL1 transcripts in patients with MPAL. This finding will bring new understandings in the diagnosis and treatment of Ph+ MPAL.

Clinicopathological differences between T-lymphoblastic leukemia/lymphoma, early T-precursor lymphoblastic leukemia/lymphoma, and mixed-phenotype acute leukemia with T lineage: an analysis of 41 adult cases.

The histopathological diagnosis of T-lymphoblastic leukemia/lymphoma, NOS (T-ALL), is based on morphology and positivity for CD3 and TdT. Early T-precursor lymphoblastic leukemia/lymphoma (ETP-ALL) and mixed-phenotype acute leukemia (MPAL), T/M, and/or B rarely occur and are usually diagnosed using flow cytometry. Using only formalin-fixed paraffin-embedded tissue raises the risk of misdiagnosis due to underestimation. Immunostaining markers for T cell (CD1a, CD4, CD5, CD8), B cell (CD19, CD10, CD22, CD79a), and stem/myeloid-related cell (CD33, CD34, CD117, MPO, lysozyme) diagnosed 25 T-ALL cases (61%), 7 MPAL (17%), 6 ETP-ALL (15%), and 3 near ETP-ALL (7%), with subsequent analysis of their clinicopathological characteristics. Patients with MPAL had significantly poorer 2-year progression-free survival (14.3% vs. 60.4%, P = 0.012) and 5-year overall survival (28.6% vs. 65.9%, P = 0.011) than did those with T-ALL, whereas ETP-ALL and near ETP-ALL did not. Of the seven patients with MPAL, three were classified as T/B, two as T/M, and two as T/M/B. Because most MPALs (6/7) share the ETP-ALL phenotype, immunohistochemistry for CD19 and MPO should be performed to avoid misdiagnosing MPAL as ETP-ALL. All three patients with TdT-negative MPAL died of the disease. Four patients with MPO-positive MPAL relapsed during the early phase (1-9 months). Five patients received the ALL regimen, but two patients received acute myeloid leukemia and lymphoma regimens, respectively. In this study, MPAL exhibited a poorer prognosis compared to T-ALL, unlike ETP-ALL. Thus, immunohistochemical classification with multiple antibody panels is useful for accurate diagnosis and treatment.

A hybrid protocol CLAG-M, a possible player for the first-line therapy of patients with mixed phenotype acute leukemia. A Polish Adult Leukemia Group experience.

Introduction: Mixed-phenotype acute leukemia (MPAL) is a rare disease with poor prognosis. So far, no standard approach has been established as the "know-how" of MPAL is based only on retrospective analyses performed on small groups of patients. Materials and methods: In this study, a retrospective analysis of the outcomes of adult MPAL patients included in the PALG registry between 2005 and 2024 who received the CLAG-M hybrid protocol as induction or salvage therapy was performed. Results: Sixteen of 98 MPAL patients received CLAG-M: eight as first-line and eight as salvage therapy. In the first line, two patients achieved partial response (PR), and six achieved complete remission (CR), of whom four successfully underwent allogeneic hematopoietic stem cell transplantation (alloHSCT). Two patients who did not undergo alloHSCT promptly relapsed. Within the whole group, the overall response rate (ORR) was 75% (n = 12/16). With the median follow-up of 13 months, six out of eight patients remain in CR, however, two of them died due to acute graft versus host disease. Out of eight patients who received CLAG-M in the second line, four patients (50%) obtained CR. AlloHSCT was conducted in seven cases, six of which were in CR. Only two patients remained in CR at the time of the last follow-up. Tolerance to treatment was good. The median times for severe neutropenia and thrombocytopenia were 22 days (range, 16-24) and 17 days (range, 12-24), respectively. Overall, grade 3-4 infections were observed in 12 cases, and all infections presented successful outcomes. Conclusions: CLAG-M is an effective first-line salvage regimen for MPAL with an acceptable safety profile. Early achievement of CR with prompt alloHSCT allows for satisfactory disease control.

[Analysis of Risk Factors for Pulmonary Infection in Patients with Acute Leukemia after Chemotherapy].

OBJECTIVE: To investigate the risk factors of pulmonary infection in patients with acute leukemia (AL) after chemotherapy. METHODS: A total of 294 patients with AL were collected and divided into infection group (n=93) and control group (n=201) according to whether the pulmonary infection occurred after chemotherapy. Analyze the correlation between sociodemographic data (sex, age, BMI), clinical data (disease type, ECOG score, invasive procedure, underlying disease, hormone therapy, empirical use of antibiotics, prognosis stratification, chemotherapy intensity, primitive cell count, white blood cell count, neutrophil count, duration of granulocyte deficiency, platelet count, hemoglobin, and albumin and pulmonary infection after chemotherapy. COX regression method was used to analyze the risk factors of pulmonary infection in AL patients after chemotherapy. RESULTS: Among 294 patients with AL, 11 died within 30 days after pulmonary infection. There were statistically significant differences in age, smoking history, ECOG score, invasive procedure, hormone therapy, empirical use of antibiotics, prognosis stratification, chemotherapy intensity, primitive cell count, neutrophil count, duration of granulocyte deficiency, platelet count, hemoglobin, albumin and fasting blood glucose between the 2 groups (P <0.05). COX regression analysis showed that smoking history, invasive procedure, unexperienced use of antibiotics, poor prognosis, long duration of granulocytopenia, low platelet level and low albumin were high risk factors for pulmonary infection in AL patients after chemotherapy (P <0.05). CONCLUSION: Smoking, invasive procedures, unexperienced use of antibiotics, poor prognosis, long duration of granulodeficiency, low platelet levels and low albumin are risk factors for pulmonary infection in AL patients after chemotherapy.

Biologic and Clinical Characteristics of Isochromosome der(17)(q10)t(15;17) in Acute Promyelocytic Leukemia.

INTRODUCTION: Acute promyelocytic leukemia (APL) is genetically characterized by the fusion of promyelocytic leukemia (PML) gene with retinoic acid receptor alpha (RARα) resulting from a t(15;17)(q24;q21) chromosomal translocation. An infrequent but recurrent finding in APL is the formation of an isochromosome of the derivative chromosome 17; ider(17)(q10)t(15;17) or ider(17q). This rearrangement in APL results in an additional copy of the PML-RARα fusion gene as well as loss of 17p/TP53. Due to the infrequent occurrence of the ider(17q), the prognostic impact of this genetic finding is not well known. Case Presentation(s): Here, we describe the clinical characteristics and outcomes of our case series of 5 patients with ider(17q) APL treated at the University of Maryland and Johns Hopkins University. CONCLUSION: In our series, patients with APL with ider(17q) did not have a worse prognosis.

The tumour suppressor Fat1 is dispensable for normal murine hematopoiesis.

Loss and overexpression of FAT1 occurs among different cancers with these divergent states equated with tumor suppressor and oncogene activity, respectively. Regarding the latter, FAT1 is highly expressed in a high proportion of human acute leukemias relative to normal blood cells, with evidence pointing to an oncogenic role. We hypothesized that this occurrence represents legacy expression of FAT1 in undefined hematopoietic precursor subsets that is sustained following transformation, predicating a role for FAT1 during normal hematopoiesis. We explored this concept by using the Vav-iCre strain to construct conditional knockout (cKO) mice where Fat1 expression was deleted at the hematopoietic stem cell stage. Extensive analysis of precursor and mature blood populations using multi-panel flow cytometry revealed no ostensible differences between Fat1 cKO mice and normal littermates. Further functional comparisons involving colony forming unit and competitive bone marrow transplantation assays support the conclusion that Fat1 is dispensable for normal murine hematopoiesis.

Single vs double umbilical cord blood transplantation in acute leukemia: Systematic review and meta-analysis.

BACKGROUND AND AIMS: Umbilical cord blood transplantation (UCBT) has emerged as a promising treatment option for patients with acute leukemia needing hematopoietic stem cell transplantation. Both single (sUCBT) and double cord blood units (dUCBT) demonstrate potential benefits, but studies comparing their effectiveness have shown mixed results. This meta-analysis aimed to determine the comparative safety and efficacy of sUCBT versus dUCBT in acute leukemia patients. METHODS: Electronic databases were systematically examined to identify relevant studies comparing single vs double UCBT published until November 2023. Nine studies involving 3864 acute leukemia patients undergoing UCBT were included. Outcomes analyzed were acute graft-versus-host disease (GVHD), chronic GVHD, relapse, non-relapse mortality, leukemia-free survival and overall survival. Pooled risk ratios (RR) with 95% confidence intervals (CI) were calculated using a random effects model. RESULTS: The risk of Grade II-IV acute GVHD (RR 1.55, 95% CI 1.19-2.03) and Grade III-IV acute GVHD (RR 1.25, 95% CI 1.07-1.46) were significantly higher with dUCBT. Relapse risk was lower with dUCBT (RR 0.57, 95% CI 0.38-0.88) while overall survival favored sUCBT (RR 1.25, 95% CI 1.06-1.46). No significant differences were observed for chronic GVHD, non-relapse mortality or leukemia-free survival. CONCLUSION: Both single and double UCBT have potential as effective treatments for acute leukemia. The choice of treatment should consider various factors, including the risk of GVHD, relapse, and mortality. More research, especially randomized trials, is needed to provide definitive guidance on the optimal use of single and double unit UCBT in patients with acute leukemia.