Pediatric Mixed-Phenotype Acute Leukemia: What's New?

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.

Biological Markers of High-Risk Childhood Acute Lymphoblastic Leukemia

Childhood acute lymphoblastic leukemia (ALL) has witnessed substantial improvements in prognosis; however, a subset of patients classified as high-risk continues to face higher rates of relapse and increased mortality. While the National Cancer Institute (NCI) criteria have traditionally guided risk stratification based on initial clinical information, recent advances highlight the pivotal role of biological markers in shaping the prognosis of childhood ALL. This review delves into the emerging understanding of high-risk childhood ALL, focusing on molecular, cytogenetic, and immunophenotypic markers. These markers not only contribute to unraveling the underlying mechanisms of the disease, but also shed light on specific clinical patterns that dictate prognosis. The paradigm shift in treatment strategies, exemplified by the success of tyrosine kinase inhibitors in Philadelphia chromosome-positive leukemia, underscores the importance of recognizing and targeting precise risk factors. Through a comprehensive exploration of high-risk childhood ALL characteristics, this review aims to enhance our comprehension of the disease, offering insights into its molecular landscape and clinical intricacies in the hope of contributing to future targeted and tailored therapies.

The Outcome of Pediatric Philadelphia Chromosome-Positive Acute Lymphoblastic Leukemia: Experience from a Referral Center in South India

Although improved survival in children with Philadelphia chromosome-positive acute lymphoblastic leukemia (Ph-ALL) has been demonstrated in trials, the outcome appears to be inferior in low- and middle-income countries (LMIC). Methods A file review of children aged ≤ 15 years diagnosed with Ph-ALL from 2010 to 2019 was performed. Minimal residual disease (MRD) was assessed by flow-cytometry. Real-time polymerase chain reaction (qRT-PCR) was used to quantify the BCR::ABL1 transcripts during treatment. Results The mean age of the 20 patients in the study was 91 months. Of 19 patients in whom the BCR::ABL1 transcript was confirmed, 10(50%) had P210, 7(35%) had P190, and two showed dual expression. The mean dose of imatinib that was administered was 294 ± 41 mg/m2/day. qRT-PCR for BCR::ABL1 was < 0.01% in all patients who were in remission or had a late relapse and was ≥ 0.01% in patients who had an early relapse. Two patients underwent HSCT. The 3-year event-free survival (EFS) was 35.0 ± 10.7%. Patients with a good prednisolone response (GPR) and a negative end-of-induction MRD demonstrated a superior EFS to those who lacked either or both (80.0 ± 17.9% vs. 16.7 ± 15.2%, P = 0.034). Conclusion The 3-year EFS of 20 children with Ph-ALL treated with chemotherapy and TKI was < 50%. An unusually high proportion of patients with p210 transcript expression; sub-optimal TKI dosing and lesser intensity of chemotherapy, due to the concern of high treatment-related mortality in LMIC are possible reasons for the poor outcome. Conventional treatment response parameters such as GPR and MRD predict outcomes in Ph-ALL. qRT-PCR for BCR::ABL1 may have a role in predicting early relapse.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12288-023-01684-9.

Genetic Characterization of Pediatric Mixed Phenotype Acute Leukemia (MPAL)

BACKGROUND/AIM

Mixed phenotype acute leukemia (MPAL) is a rare hematologic malignancy in which the leukemic cells cannot be assigned to any specific lineage. The lack of well-defined, pathogenetically relevant diagnostic criteria makes the clinical handling of MPAL patients challenging. We herein report the genetic findings in bone marrow cells from two pediatric MPAL patients.

PATIENTS AND METHODS

Bone marrow cells were examined using G-banding, array comparative genomic hybridization, RNA sequencing, reverse transcription polymerase chain reaction, Sanger sequencing, and fluorescence in situ hybridization.

RESULTS

In the first patient, the genetic analyses revealed structural aberrations of chromosomal bands 8p11, 10p11, 11q21, and 17p11, the chimeras MLLT10::PICALM and PICALM::MLLT10, and imbalances (gains/losses) on chromosomes 2, 4, 8, 13, and 21. A submicroscopic deletion in 21q was also found including the RUNX1 locus. In the second patient, there were structural aberrations of chromosome bands 1p32, 8p11, 12p13, 20p13, and 20q11, the chimeras ETV6::LEXM and NCOA6::ETV6, and imbalances on chromosomes 2, 8, 11, 12, 16, 19, X, and Y.

CONCLUSION

The leukemic cells from both MPAL patients carried chromosome aberrations resulting in fusion genes as well as genomic imbalances resulting in gain and losses of many gene loci. The detected fusion genes probably represent the main leukemogenic events, although the gains and losses are also likely to play a role in leukemogenesis.

Estimating the prevalence of pediatric hematological malignancies in Al-Madinah Al-Munawwarah, Saudi Arabia

OBJECTIVES

To provide an updated estimate to the prevalence of pediatric hematological malignancies (HMs) in the Al-Madinah Al-Munawwara, Saudi Arabia.

METHODS

This is a retrospective study that was carried out between 2016 and 2022. The study population was comprised of 171 children under 16 who had been diagnosed with HMs. The data was compiled from King Salman Medical City's Maternity and Children's Hospital, Al-Madinah Al-Munawwarah, Saudi Arabia.

RESULTS

Among the 171 HM patients (64% males and 36% females), 13 subtypes were identified, with B-cell acute lymphoblastic leukemia having the highest incidence (70.3%). Acute myelomonocytic leukemia (8.7%), T-cell acute lymphoblastic leukemia (4.7%), and acute promyelocytic leukemia (3.5%) were the next most common types of HMs. Other rare cases were also found.

CONCLUSION

Prevalence rate can be utilized to monitor the progression of disease incidence. Here, HMs demonstrated a pattern of increasing incidence in males over a 7-year period, with a higher rate in early childhood. There were 13 types of HMs diagnosed, with B-acute lymphocytic leukemia having the highest incidence. Although juvenile cancer is rare, it is nonetheless a significant cause of mortality in children. A successful prognosis requires prompt and accurate diagnosis and treatment.

Mixed Phenotype/Lineage Leukemia: Has Anything Changed for 2021 on Diagnosis, Classification, and Treatment?

Purpose of Review

Recent advances in the small field of the rare mixed phenotype acute leukemias (MPAL) are presented focusing on a better understanding of their pathophysiology and search for better therapeutic approaches.

Recent Findings

Three aspects of respective classification, therapy, and immunophenotype of MPAL are reviewed. New proposals have been made to segregate MPAL subtypes based on their genomic landscape. In parallel, it was found that a large array of therapeutic approaches has been tested in the past few years with increasingly good results. Finally, we explored the use of unsupervised flow cytometry analysis to dissect subtle variations in markers expression to better characterize the variegating aspect of MPALs.

Summary

Genomic and immunophenotypic aspects more clearly link MPAL subtypes with bona fide acute myeloblastic of lymphoblastic leukemias. This is likely to impact therapeutic strategies, towards a better management and outcome.

Lineage Conversion in Pediatric B-Cell Precursor Acute Leukemia under Blinatumomab Therapy

We report incidence and deep molecular characteristics of lineage switch in 182 pediatric patients affected by B-cell precursor acute lymphoblastic leukemia (BCP-ALL), who were treated with blinatumomab. We documented six cases of lineage switch that occurred after or during blinatumomab exposure. Therefore, lineage conversion was found in 17.4% of all resistance cases (4/27) and 3.2% of relapses (2/63). Half of patients switched completely from BCP-ALL to CD19-negative acute myeloid leukemia, others retained CD19-positive B-blasts and acquired an additional CD19-negative blast population: myeloid or unclassifiable. Five patients had KMT2A gene rearrangements; one had TCF3::ZNF384 translocation. The presented cases showed consistency of gene rearrangements and fusion transcripts across initially diagnosed leukemia and lineage switch. In two of six patients, the clonal architecture assessed by IG/TR gene rearrangements was stable, while in others, loss of clones or gain of new clones was noted. KMT2A-r patients demonstrated very few additional mutations, while in the TCF3::ZNF384 case, lineage switch was accompanied by a large set of additional mutations. The immunophenotype of an existing leukemia sometimes changes via different mechanisms and with different additional molecular changes. Careful investigation of all BM compartments together with all molecular -minimal residual disease studies can lead to reliable identification of lineage switch.

Increasing Complexity of Molecular Landscapes in Human Hematopoietic Stem and Progenitor Cells during Development and Aging

The past five decades have seen significant progress in our understanding of human hematopoiesis. This has in part been due to the unprecedented development of advanced technologies, which have allowed the identification and characterization of rare subsets of human hematopoietic stem and progenitor cells and their lineage trajectories from embryonic through to adult life. Additionally, surrogate in vitro and in vivo models, although not fully recapitulating human hematopoiesis, have spurred on these scientific advances. These approaches have heightened our knowledge of hematological disorders and diseases and have led to their improved diagnosis and therapies. Here, we review human hematopoiesis at each end of the age spectrum, during embryonic and fetal development and on aging, providing exemplars of recent progress in deciphering the increasingly complex cellular and molecular hematopoietic landscapes in health and disease. This review concludes by highlighting links between chronic inflammation and metabolic and epigenetic changes associated with aging and in the development of clonal hematopoiesis.