Clonal evolution and clinical implications of genetic abnormalities in blastic transformation of chronic myeloid leukaemia

Chronic myeloid leukemia: 2025 update on diagnosis, therapy, and monitoring

DISEASE OVERVIEW

Chronic myeloid leukemia (CML) is a myeloproliferative neoplasm with an annual incidence of two cases/100 000. It accounts for approximately 15% of newly diagnosed cases of leukemia in adults.

DIAGNOSIS

CML is characterized by a balanced genetic translocation, t(9;22) (q34;q11.2), involving a fusion of the Abelson murine leukemia (ABL1) gene from chromosome 9q34 with the breakpoint cluster region (BCR) gene on chromosome 22q11.2. This rearrangement is known as the Philadelphia chromosome. The molecular consequence of this translocation is the generation of a BCR::ABL1 fusion oncogene, which in turn translates into a BCR::ABL1 oncoprotein.

FRONTLINE THERAPY

Four tyrosine kinase inhibitors (TKIs), imatinib, dasatinib, bosutinib, and nilotinib, are approved by the United States Food and Drug Administration (FDA) for first-line treatment of newly diagnosed CML in the chronic phase (CML-CP). Clinical trials with second and third-generation TKIs in frontline CML-CP therapy reported significantly deeper and faster responses but had no impact on survival prolongation, likely because of their potent efficacy and the availability of effective TKIs salvage therapies for patients who have a cytogenetic relapse with frontline TKI therapy. All four TKIs are equivalent if the aim of therapy is to improve survival. In younger patients with high-risk disease and in whom the aim of therapy is to induce a treatment-free remission status, second-generation TKIs may be favored.

SALVAGE THERAPY

For CML post-failure on frontline therapy, second-line options include second and third-generation TKIs. Although potent and selective, these TKIs exhibit unique pharmacological profiles and response patterns relative to different patient and disease characteristics, such as patients' comorbidities and financial status, disease stage, and BCR::ABL1 mutational status. Patients who develop the T315I "gatekeeper" mutation display resistance to all currently available TKIs except ponatinib, asciminib, and olverembatinib. Allogeneic stem cell transplantation remains an important therapeutic option for patients with CML-CP and failure (due to resistance) of at least two TKIs and for all patients in advanced-phase disease. Older patients who have a cytogenetic relapse post-failure on all TKIs can maintain long-term survival if they continue a daily most effective/least toxic TKI, with or without the addition of non-TKI anti-CML agents (hydroxyurea, omacetaxine, azacitidine, decitabine, cytarabine, and others).

miR-15a targets the HSP90 co-chaperone Morgana in chronic myeloid leukemia

Morgana is a ubiquitous HSP90 co-chaperone protein coded by the CHORDC1 gene. Morgana heterozygous mice develop with age a myeloid malignancy resembling human atypical myeloid leukemia (aCML), now renamed MDS/MPN with neutrophilia. Patients affected by this pathology exhibit low Morgana levels in the bone marrow (BM), suggesting that Morgana downregulation plays a causative role in the human malignancy. A decrease in Morgana expression levels is also evident in the BM of a subgroup of Philadelphia-positive (Ph+) chronic myeloid leukemia (CML) patients showing resistance or an incomplete response to imatinib. Despite the relevance of these data, the mechanism through which Morgana expression is downregulated in patients' bone marrow remains unclear. In this study, we investigated the possibility that Morgana expression is regulated by miRNAs and we demonstrated that Morgana is under the control of four miRNAs (miR-15a/b and miR-26a/b) and that miR-15a may account for Morgana downregulation in CML patients.

Precision Diagnostics in Myeloid Malignancies: Development and Validation of a National Capture-Based Gene Panel

Gene panel sequencing has become a common diagnostic tool for detecting somatically acquired mutations in myeloid neoplasms. However, many panels have restricted content, provide insufficient sensitivity levels, or lack clinically validated workflows. We here describe the development and validation of the Genomic Medicine Sweden myeloid gene panel (GMS-MGP), a capture-based 191 gene panel including mandatory genes in contemporary guidelines as well as emerging candidates. The GMS-MGP displayed uniform coverage across all targets, including recognized difficult GC-rich areas. The validation of 117 previously described somatic variants showed a 100% concordance with a limit-of-detection of a 0.5% variant allele frequency (VAF), achieved by utilizing error correction and filtering against a panel-of-normals. A national interlaboratory comparison investigating 56 somatic variants demonstrated highly concordant results in both detection rate and reported VAFs. In addition, prospective analysis of 323 patients analyzed with the GMS-MGP as part of standard-of-care identified clinically significant genes as well as recurrent mutations in less well-studied genes. In conclusion, the GMS-MGP workflow supports sensitive detection of all clinically relevant genes, facilitates novel findings, and is, based on the capture-based design, easy to update once new guidelines become available. The GMS-MGP provides an important step toward nationally harmonized precision diagnostics of myeloid malignancies.

DNA damage response defects in hematologic malignancies: mechanistic insights and therapeutic strategies

ABSTRACT

The DNA damage response (DDR) encompasses the detection and repair of DNA lesions and is fundamental to the maintenance of genome integrity. Germ line DDR alterations underlie hereditary chromosome instability syndromes by promoting the acquisition of pathogenic structural variants in hematopoietic cells, resulting in increased predisposition to hematologic malignancies. Also frequent in hematologic malignancies are somatic mutations of DDR genes, typically arising from replication stress triggered by oncogene activation or deregulated tumor proliferation that provides a selective pressure for DDR loss. These defects impair homology-directed DNA repair or replication stress response, leading to an excessive reliance on error-prone DNA repair mechanisms that results in genomic instability and tumor progression. In hematologic malignancies, loss-of-function DDR alterations confer clonal growth advantage and adverse prognostic impact but may also provide therapeutic opportunities. Selective targeting of functional dependencies arising from these defects could achieve synthetic lethality, a therapeutic concept exemplified by inhibition of poly-(adenosine 5'-diphosphate ribose) polymerase or the ataxia telangiectasia and Rad 3 related-CHK1-WEE1 axis in malignancies harboring the BRCAness phenotype or genetic defects that increase replication stress. Furthermore, the role of DDR defects as a source of tumor immunogenicity, as well as their impact on the cross talk between DDR, inflammation, and tumor immunity are increasingly recognized, thus providing rationale for combining DDR modulation with immune modulation. The nature of the DDR-immune interface and the cellular vulnerabilities conferred by DDR defects may nonetheless be disease-specific and remain incompletely understood in many hematologic malignancies. Their comprehensive elucidation will be critical for optimizing therapeutic strategies to target DDR defects in these diseases.

Management and outcome of patients with chronic myeloid leukemia in blast phase in the tyrosine kinase inhibitor era - analysis of the European LeukemiaNet Blast Phase Registry

Blast phase (BP) of chronic myeloid leukemia (CML) still represents an unmet clinical need with a dismal prognosis. Due to the rarity of the condition and the heterogeneity of the biology and clinical presentation, prospective trials and concise treatment recommendations are lacking. Here we present the analysis of the European LeukemiaNet Blast Phase Registry, an international collection of the clinical presentation, treatment and outcome of blast phases which had been diagnosed in CML patients after 2015. Data reveal the expected heterogeneity of the entity, lacking a clear treatment standard. Outcomes remain dismal, with a median overall survival of 23.8 months (median follow up 27.8 months). Allogeneic stem cell transplantation (alloSCT) increases the rate of deep molecular responses. De novo BP and BP evolving from a previous CML do show slightly different features, suggesting a different biology between the two entities. Data show that outside clinical trials and in a real-world setting treatment of blast phase is individualized according to disease- and patient-related characteristics, with the aim of blast clearance prior to allogeneic stem cell transplantation. AlloSCT should be offered to all patients eligible for this procedure.

[Clinical analysis of allogeneic hematopoietic stem cell transplantation for seven cases of acute myeloid leukemia with BCR::ABL1 fusion]

Objective: To explore the efficacy of allogeneic hematopoietic stem cell transplantation (allo-HSCT) in acute myeloid leukemia (AML) patients with BCR::ABL1 fusion. Methods: The clinical data of seven AML patients with BCR::ABL1 fusion from November 2012 to January 2022 were retrospectively analyzed, and their survival status was followed up. Results: The median age of patients at the time of diagnosis was 35 years. Four cases (57.1%) were diagnosed with high leukocyte counts. All cases were assayed as BCR::ABL1 positive and accompanied by four types of gene mutations (NPM1, RUNX1, ASXL1, PHF6) . Seven patients received tyrosine kinase inhibitor (TKI) combined with induction chemotherapy and bridged to allo-HSCT, and six patients received maintenance therapy with TKI. Before allo-HSCT, six patients achieved complete remission, and four patients achieved complete molecular remission (CMR) . After allo-HSCT, the three remaining cases also achieved CMR. All patients were in remission post-allo-HSCT. One case died of infection, and the remaining cases survived without relapse. The 3-year cumulative overall survival rate was (80.0±17.9) %. Conclusions: TKI combined with traditional chemotherapy could achieve a high response rate in AML patients with BCR::ABL1 fusion. In addition, allo-HSCT could enhance the molecular response rate. Maintenance therapy post-HSCT with TKI could improve prognosis.

Accelerated-phase CML: de novo and transformed

Despite the dramatic improvements in outcomes for the majority of chronic myeloid leukemia (CML) patients over the past 2 decades, a similar improvement has not been observed in the more advanced stages of the disease. Blast phase CML (BP-CML), although infrequent, remains poorly understood and inadequately treated. Consequently, the key initial goal of therapy in a newly diagnosed patient with chronic phase CML continues to be prevention of disease progression. Advances in genomic investigation in CML, specifically related to BP-CML, clearly demonstrate we have only scratched the surface in our understanding of the disease biology, a prerequisite to devising more targeted and effective therapeutic approaches to prevention and treatment. Importantly, the introduction of the concept of "CML-like" acute lymphoblastic leukemia (ALL) has the potential to simplify the differentiation between BCR::ABL1-positive ALL from de novo lymphoid BP-CML, optimizing monitoring and therapeutics. The development of novel treatment strategies such as the MATCHPOINT approach for BP-CML, utilizing combination chemotherapy with fludarabine, cytarabine, and idarubicin in addition to dose-modified ponatinib, may also be an important step in improving treatment outcomes. However, identifying patients who are high risk of transformation remains a challenge, and the recent 2022 updates to the international guidelines may add further confusion to this area. Further work is required to clarify the identification and treatment strategy for the patients who require a more aggressive approach than standard chronic phase CML management.

European LeukemiaNet laboratory recommendations for the diagnosis and management of chronic myeloid leukemia

From the laboratory perspective, effective management of patients with chronic myeloid leukemia (CML) requires accurate diagnosis, assessment of prognostic markers, sequential assessment of levels of residual disease and investigation of possible reasons for resistance, relapse or progression. Our scientific and clinical knowledge underpinning these requirements continues to evolve, as do laboratory methods and technologies. The European LeukemiaNet convened an expert panel to critically consider the current status of genetic laboratory approaches to help diagnose and manage CML patients. Our recommendations focus on current best practice and highlight the strengths and pitfalls of commonly used laboratory tests.

Deciphering Potential Molecular Signatures to Differentiate Acute Myeloid Leukemia (AML) with BCR::ABL1 from Chronic Myeloid Leukemia (CML) in Blast Crisis

Acute myeloid leukemia (AML) with BCR::ABL1 has recently been recognized as a distinct subtype in international classifications. Distinguishing it from myeloid blast crisis chronic myeloid leukemia (BC-CML) without evidence of a chronic phase (CP), remains challenging. We aimed to better characterize this entity by integrating clonal architecture analysis, mutational landscape assessment, and gene expression profiling. We analyzed a large retrospective cohort study including CML and AML patients. Two AML patients harboring a BCR::ABL1 fusion were included in the study. We identified BCR::ABL1 fusion as a primary event in one patient and a secondary one in the other. AML-specific variants were identified in both. Real-time RT-PCR experiments demonstrated that CD25 mRNA is overexpressed in advanced-phase CML compared to AML. Unsupervised principal component analysis showed that AML harboring a BCR::ABL1 fusion was clustered within AML. An AML vs. myeloid BC-CML differential expression signature was highlighted, and while ID4 (inhibitor of DNA binding 4) mRNA appears undetectable in most myeloid BC-CML samples, low levels are detected in AML samples. Therefore, CD25 and ID4 mRNA expression might differentiate AML with BCR::ABL1 from BC-CML and assign it to the AML group. A method for identifying this new WHO entity is then proposed. Finally, the hypothesis of AML with BCR::ABL1 arising from driver mutations on a BCR::ABL1 background behaving as a clonal hematopoiesis mutation is discussed. Validation of our data in larger cohorts and basic research are needed to better understand the molecular and cellular aspects of AML with a BCR::ABL1 entity.

Cytogenetics in the management of myeloproliferative neoplasms, mastocytosis and myelodysplastic/myeloproliferative neoplasms: Guidelines from the Group Francophone de Cytogénétique Hématologique (GFCH)

Myeloproliferative neoplasms, mastocytosis, myeloid/lymphoid neoplasms with hypereosinophilia and tyrosine kinase gene fusions, and myelodysplastic/myeloproliferative neoplasms are clonal hematopoietic cancers that, with the exception of certain entities, have an indolent course. In addition to their increasingly important role in the diagnosis of these entities, as shown by the recent classification of hematolymphoid tumors in the 5th edition of the World Health Organization and the International Consensus Classification of myeloid neoplasms and acute leukemias, identification of the profile of acquired genetic abnormalities is essential for adapting patient management and early detection of patients at high risk of progression. Alongside molecular abnormalities, cytogenetic abnormalities play an important role in the diagnosis, prognosis and follow-up of these diseases. Here, we review the recent literature on the impact of chromosomal abnormalities in these different entities and provide updated cytogenetic recommendations and guidelines for their management.

Impact of additional genetic abnormalities at diagnosis of chronic myeloid leukemia for first-line imatinib-treated patients receiving proactive treatment intervention

The BCR::ABL1 gene fusion initiates chronic myeloid leukemia (CML); however, evidence has accumulated from studies of highly selected cohorts that variants in other cancer-related genes are associated with treatment failure. Nevertheless, the true incidence and impact of additional genetic abnormalities (AGA) at diagnosis of chronic phase (CP)-CML is unknown. We sought to determine whether AGA at diagnosis in a consecutive imatinib-treated cohort of 210 patients enrolled in the TIDEL-II trial influenced outcome despite a highly proactive treatment intervention strategy. Survival outcomes including overall survival, progression-free survival, failure-free survival, and BCR::ABL1 kinase domain mutation acquisition were evaluated. Molecular outcomes were measured at a central laboratory and included major molecular response (MMR, BCR::ABL1 ≤0.1%IS), MR4 (BCR::ABL1 ≤0.01%IS), and MR4.5 (BCR::ABL1 ≤0.0032%IS). AGA included variants in known cancer genes and novel rearrangements involving the formation of the Philadelphia chromosome. Clinical outcomes and molecular response were assessed based on the patient's genetic profile and other baseline factors. AGA were identified in 31% of patients. Potentially pathogenic variants in cancer-related genes were detected in 16% of patients at diagnosis (including gene fusions and deletions) and structural rearrangements involving the Philadelphia chromosome (Ph-associated rearrangements) were detected in 18%. Multivariable analysis demonstrated that the combined genetic abnormalities plus the EUTOS long-term survival clinical risk score were independent predictors of lower molecular response rates and higher treatment failure. Despite a highly proactive treatment intervention strategy, first-line imatinib-treated patients with AGA had poorer response rates. These data provide evidence for the incorporation of genomically-based risk assessment for CML.

Presence of Myeloid Mutations in Patients with Chronic Myeloid Leukemia Increases Risk of Cardiovascular Event on Tyrosine Kinase Inhibitor Treatment

For chronic myeloid leukemia (CML) patients with a known risk of cardiovascular events (CVE), imatinib is often recommended for first-line tyrosine kinase inhibitor (TKI) treatment rather than a second-generation TKI (2G-TKI) such as nilotinib or dasatinib. To date, very few studies have evaluated the genetic predisposition associated with CVE development on TKI treatment. In this retrospective study of 102 CML patients, 26 CVEs were reported during an average follow-up of over 10 years. Next-generation sequencing identified pathogenic/likely pathogenic mutations in genes associated with myeloid malignancies in 24.5% of the diagnostic samples analyzed. Patients with a recorded CVE had more myeloid mutations (0.48 vs. 0.14, p = 0.019) and were older (65.1 vs. 55.7 years, p = 0.016). Age ≥ 60 years and receiving a 2G-TKI in first-line were CVE risk factors. The presence of a pathogenic somatic myeloid mutation was an independent risk factor for CVE on any TKI (HR 2.79, p = 0.01), and significantly shortened the CV event-free survival of patients who received first-line imatinib (by 70 months, p = 0.011). Indeed, 62% of patients on imatinib with mutations had a CVE vs. the 19% on imatinib with a mutation and no CVE. In conclusion, myeloid mutations detectable at diagnosis increase CVE risk, particularly for patients on imatinib, and might be considered for first-line TKI choice.

Clonal evolution in tyrosine kinase inhibitor-resistance: lessons from in vitro-models

Introduction

Resistance in anti-cancer treatment is a result of clonal evolution and clonal selection. In chronic myeloid leukemia (CML), the hematopoietic neoplasm is predominantly caused by the formation of the BCR::ABL1 kinase. Evidently, treatment with tyrosine kinase inhibitors (TKIs) is tremendously successful. It has become the role model of targeted therapy. However, therapy resistance to TKIs leads to loss of molecular remission in about 25% of CML patients being partially due to BCR::ABL1 kinase mutations, while for the remaining cases, various other mechanisms are discussed.

Methods

Here, we established an in vitro-TKI resistance model against the TKIs imatinib and nilotinib and performed exome sequencing.

Results

In this model, acquired sequence variants in NRAS, KRAS, PTPN11, and PDGFRB were identified in TKI resistance. The well-known pathogenic NRAS p.(Gln61Lys) variant provided a strong benefit for CML cells under TKI exposure visible by increased cell number (6.2-fold, p < 0.001) and decreased apoptosis (-25%, p < 0.001), proving the functionality of our approach. The transfection of PTPN11 p.(Tyr279Cys) led to increased cell number (1.7-fold, p = 0.03) and proliferation (2.0-fold, p < 0.001) under imatinib treatment.

Discussion

Our data demonstrate that our in vitro-model can be used to study the effect of specific variants on TKI resistance and to identify new driver mutations and genes playing a role in TKI resistance. The established pipeline can be used to study candidates acquired in TKI-resistant patients, thereby providing new options for the development of new therapy strategies to overcome resistance.

Molecular Evaluation of the Impact of Polymorphic Variants in Apoptotic (Bcl-2/Bax) and Proinflammatory Cytokine (TNF-α/IL-8) Genes on the Susceptibility and Progression of Myeloproliferative Neoplasms: A Case-Control Biomarker Study

The regulation of apoptosis (the programmed cell death) is dependent on the crucial involvement of BCL2 and BAX. The Bax-248G>A and Bcl-2-938 C>A polymorphic variations in the promoter sequences of the Bax and Bcl-2 gene have been recently associated with low Bax expression, progression to advanced stages, treatment resistance, and shortened overall survival rate in some hematological malignancies, including chronic myeloid leukemia (CML) and other myeloproliferative neoplasms. Chronic inflammation has been linked to various stages of carcinogenesis wherein pro-inflammatory cytokines play diverse roles in influencing cancer microenvironment leading to cell invasion and cancer progression. Cytokines such as TNF-α and IL-8 have been implicated in cancer growth in both solid and hematological malignancies with studies showing their elevated levels in patients. Genomic approaches have in recent years provided significant knowledge with the regard to the association of certain SNPs (single nucleotide polymerphisms) either in a gene or its promoter that can influence its expression, with the risk and susceptibility to human diseases including cancer. This study has investigated the consequences of promoter SNPs in apoptosis genes Bax-248G>A (rs4645878)/Bcl-2-938C>A (rs2279115) and pro-inflammatory cytokines TNF-α rs1800629 G>A/IL-8 rs4073 T>A on the risk and susceptibility towards hematological cancers. The study design has 235 individuals both male and female enrolled as subjects that had 113 cases of MPDs (myeloproliferative disorders) and 122 healthy individuals as controls. The genotyping studies were conducted through ARMS PCR (amplification-refractory mutation system PCR). The Bcl-2-938 C>A polymorphism showed up in 22% of patients in the study, while it was observed in only 10% of normal controls. This difference in genotype and allele frequency between the two groups was significant (p = 0.025). Similarly, the Bax-248G>A polymorphism was detected in 6.48% of the patients and 4.54% of the normal controls, with a significant difference in genotype and allele frequency between the groups (p = 0.048). The results suggest that the Bcl-2-938 C>A variant is linked to an elevated risk of MPDs in the codominant, dominant, and recessive inheritance models. Moreover, the study indicated allele A as risk allele which can significantly increase the risk of MPDs unlike the C allele. In case of Bax gene covariants, these were associated with an increased risk of MPDs in the codominant inheritance model and dominant inheritance model. It was found that the allele A significantly enhanced the risk of MPDs unlike the G allele. The frequencies of IL-8 rs4073 T>A in patients was found to be TT (16.39%), AT (36.88%) and AA (46.72%), compared to controls who were more likely to have frequencies of TT (39.34%), AT (37.70%) and AA (22.95%) as such, respectively. There was a notable overrepresentation of the AA genotype and GG homozygotes among patients compared to controls in TNF-α polymorphic variants, with 6.55% of patients having the AA genotype and 84% of patients being GG homozygotes, compared to 1.63% and 69%, respectively in controls. The data from the current study provide partial but important evidence that polymorphisms in apoptotic genes Bcl-2-938C>A and Bax-248G>A and pro-inflammatory cytokines IL-8 rs4073 T>A and TNF-α G>A may help predict the clinical outcomes of patients and determine the significance of such polymorphic variations in the risk of myeloproliferative diseases and their role as prognostic markers in disease management using a case-control study approach.

Advances in molecular evaluation of myeloproliferative neoplasms

Myeloproliferative neoplasms (MPN) are a group of clonal hematopoietic stem cell disorders with uncontrolled proliferation of one or more hematopoietic cell types, including myeloid, erythroid and megakaryocytic lineages, and minimal defect in maturation. Most MPN are associated with well-defined molecular abnormalities involving genes that encode protein tyrosine kinases that lead to constitutive activation of the downstream signal transduction pathways and confer cells proliferative and survival advantage. Genome-wide sequencing analyses have discovered secondary cooperating mutations that are shared by most of the MPN subtypes as well as other myeloid neoplasms and play a major role in disease progression. Without appropriate management, the natural history of most MPN consists of an initial chronic phase and a terminal blast phase. Molecular aberrations involving protein tyrosine kinases have been used for the diagnosis, classification, detection of minimal/measurable residual disease, and target therapy. We review recent advances in molecular genetic aberrations in MPN with a focus on MPN associated with gene rearrangements or mutations involving tyrosine kinase pathways.

Case report: First report of isolated central nervous system lymphoblastic crisis in a child with chronic myeloid leukemia on dasatinib therapy

Most children with chronic myeloid leukemia (CML) present with the chronic phase (CML-CP) at diagnosis, exhibiting an excellent treatment response to contemporary tyrosine kinase inhibitors (TKIs). However, despite TKI therapy, patients with CML-CP may progress to blastic crisis (BC). CML-BC rarely occurs in extramedullary sites, and isolated central nervous system (CNS) BC is an extremely rare condition. It may with present various neurologic symptoms that necessitates differential diagnosis from other causes such as TKI toxicity. Information on the diagnosis and treatment of this condition is lacking, as are well-established diagnostic criteria. Here, we report a case of isolated CNS lymphoblastic crisis in a child with CML-CP who was treated with dasatinib. The patient, an 8-year-old girl, was admitted owing to visual disturbance and severe headache. We highlight the importance of a CSF study for the differential diagnosis of CNS BC in patients with CML-CP who present with common neurologic symptoms during TKI therapy.

Pathogenesis and management of accelerated and blast phases of chronic myeloid leukemia

The treatment of chronic myeloid leukemia (CML) with tyrosine kinase inhibitors (TKIs) has been a model for cancer therapy development. Though most patients with CML have a normal quality and duration of life with TKI therapy, some patients progress to accelerated phase (AP) and blast phase (BP), both of which have a relatively poor prognosis. The rates of progression have reduced significantly from over >20% in the pre-TKI era to <5% now, largely due to refinements in CML therapy and response monitoring. Significant insights have been gained into the mechanisms of disease transformation including the role of additional cytogenetic abnormalities, somatic mutations, and other genomic alterations present at diagnosis or evolving on therapy. This knowledge is helping to optimize TKI therapy, improve prognostication and inform the development of novel combination regimens in these patients. While patients with de novo CML-AP have outcomes almost similar to CML in chronic phase (CP), those transformed from previously treated CML-CP should receive second- or third- generation TKIs and be strongly considered for allogeneic stem cell transplantation (allo-SCT). Similarly, patients with transformed CML-BP have particularly dismal outcomes with a median survival usually less than one year. Combination regimens with a potent TKI such as ponatinib followed by allo-SCT can achieve long-term survival in some transformed BP patients. Regimens including venetoclax in myeloid BP or inotuzumab ozogamicin or blinatumomab in lymphoid BP might lead to deeper and longer responses, facilitating potentially curative allo-SCT for patients with CML-BP once CP is achieved. Newer agents and novel combination therapies are further expanding the therapeutic arsenal in advanced phase CML.

Genetic landscape of chronic myeloid leukemia

Chronic myeloid leukemia (CML) is a myeloproliferative neoplasm caused by the BCR::ABL1 fusion gene, which aberrantly activates ABL1 kinase and promotes the overproduction of leukemic cells. CML typically develops in the chronic phase (CP) and progresses to a blast crisis (BC) after years without effective treatment. Although prognosis has substantially improved after the development of tyrosine kinase inhibitors (TKIs) targeting the BCR::ABL1 oncoprotein, some patients still experience TKI resistance and poor prognosis. One of the mechanisms of TKI resistance is ABL1 kinase domain mutations, which are found in approximately half of the cases, newly acquired during treatment. Moreover, genetic studies have revealed that CML patients carry additional mutations that are also observed in other myeloid neoplasms. ASXL1 mutations are often found in both CP and BC, whereas other mutations, such as those in RUNX1, IKZF1, and TP53, are preferentially found in BC. The presence of additional mutations, such as ASXL1 mutations, is a potential biomarker for predicting therapeutic efficacy. The mechanisms by which these additional mutations affect disease subtypes, drug resistance, and prognosis need to be elucidated. In this review, we have summarized and discussed the landscape and clinical impact of genetic abnormalities in CML.

Chronic Myeloid Leukemia, from Pathophysiology to Treatment-Free Remission: A Narrative Literature Review

Chronic myeloid leukemia (CML) is one of the most common leukemias occurring in the adult population. The course of CML is divided into three phases: the chronic phase, the acceleration phase, and the blast phase. Pathophysiology of CML revolves around Philadelphia chromosome that constitutively activate tyrosine kinase through BCR-ABL1 oncoprotein. In the era of tyrosine kinase inhibitors (TKIs), CML patients now have a similar life expectancy to people without CML, and it is now very rare for CML patients to progress to the blast phase. Only a small proportion of CML patients have resistance to TKI, caused by BCR-ABL1 point mutations. CML patients with TKI resistance should be treated with second or third generation TKI, depending on the BCR-ABL1 mutation. Recently, many studies have shown that it is possible for CML patients who achieve a long-term deep molecular response to stop TKIs treatment and maintain remission. This review aimed to provide an overview of CML, including its pathophysiology, clinical manifestations, the role of stem cells, CML treatments, and treatment-free remission.

Molecular genetic characterization of Philadelphia chromosome-positive acute myeloid leukemia

BACKGROUND

Philadelphia chromosome-positive acute myeloid leukemia (Ph+ AML) is a provisional disease entity in the 2016 WHO classification, while its genetic profile of Ph+ AML remains poorly defined. In addition, the differentiating features of Ph+ AML and chronic myeloid leukemia in myeloid blast crisis (CML-MBC) remain controversial.

METHODS

We conducted a retrospective study of 15 Ph+ AML patients to compare their clinical and laboratory profiles with 27 CML-MBC patients.

RESULTS

Compared to CML-MBC, Ph+ AML patients presented with significantly higher peripheral WBC count and bone marrow blast percentage. The immunophenotypic profiles were largely similar between Ph+ AML and CML-MBC, except for CD4 expression, which was significantly enriched in CML-MBC. Ph+ AML patients less frequently harboured co-occurring additional cytogenetic abnormalities (ACA) compared to CML-MBC, and trisomy 19 (23%) and IDH1/2 (46%) were the most common ACA and mutated genes in Ph+ AML, respectively. Overall survival (OS) did not significantly differ between Ph+ AML and CML-MBC. Ph+ AML without CML-like features appeared to have a better outcome compared to Ph+ AML with CML-like features; ACA in Ph+ AML may confer an even worse prognosis.

CONCLUSIONS

Our results indicate that patients with Ph+ AML share similar genetic profiles and clinical outcomes with those with CML-MBC, thus should be classified as a high-risk entity.

Alterations in cellular metabolisms after TKI therapy for Philadelphia chromosome-positive leukemia in children: A review

Incidence rates of chronic myeloid leukemia (CML) and Philadelphia chromosome-positive (Ph+) acute lymphoblastic leukemia (ALL) are lower but more aggressive in children than in adults due to different biological and host factors. After the clinical application of tyrosine kinase inhibitor (TKI) blocking BCR/ABL kinase activity, the prognosis of children with CML and Ph+ ALL has improved dramatically. Yet, off-target effects and drug tolerance will occur during the TKI treatments, contributing to treatment failure. In addition, compared to adults, children may need a longer course of TKIs therapy, causing detrimental effects on growth and development. In recent years, accumulating evidence indicates that drug resistance and side effects during TKI treatment may result from the cellular metabolism alterations. In this review, we provide a detailed summary of the current knowledge on alterations in metabolic pathways including glucose metabolism, lipid metabolism, amino acid metabolism, and other metabolic processes. In order to obtain better TKI treatment outcomes and avoid side effects, it is essential to understand how the TKIs affect cellular metabolism. Hence, we also discuss the relevance of cellular metabolism in TKIs therapy to provide ideas for better use of TKIs in clinical practice.

Treatment of blast phase chronic myeloid leukaemia: A rare and challenging entity

Despite the success of BCR-ABL-specific tyrosine kinase inhibitors (TKIs) such as imatinib in chronic phase (CP) chronic myeloid leukaemia (CML), patients with blast phase (BP)-CML continue to have a dismal outcome with median survival of less than one year from diagnosis. Thus BP-CML remains a critical unmet clinical need in the management of CML. Our understanding of the biology of BP-CML continues to grow; genomic instability leads to acquisition of mutations which drive leukaemic progenitor cells to develop self-renewal properties, resulting in differentiation block and a poor-prognosis acute leukaemia which may be myeloid, lymphoid or bi-phenotypic. Similar advances in therapy are urgently needed to improve patient outcomes; however, this is challenging given the rarity and heterogeneity of BP-CML, leading to difficulty in designing and recruiting to prospective clinical trials. This review will explore the treatment of BP-CML, evaluating the data for TKI therapy alone, combinations with intensive chemotherapy, the role of allogeneic haemopoietic stem cell transplantation, the use of novel agents and clinical trials, as well as discussing the most appropriate methods for diagnosing BP and assessing response to therapy, and factors predicting outcome.

Measurable residual disease in chronic myeloid leukemia

Chronic myeloid leukemia is characterized by a single genetic abnormality resulting in a fusion gene whose mRNA product is easily detected and quantified by reverse-transcriptase polymerase chain reaction analysis. Measuring residual disease was originally introduced to identify patients relapsing after allogeneic stem cell transplantation but rapidly adopted to quantify responses to tyrosine kinase inhibitors. Real-time quantitative polymerase chain reaction is now an essential tool for the management of patients and is used to influence treatment decisions. In this review we track this development including the international collaboration to standardize results, discuss the integration of molecular monitoring with other factors that affect patients' management, and describe emerging technology. Four case histories describe varying scenarios in which the accurate measurement of residual disease identified patients at risk of disease progression and allowed appropriate investigations and timely clinical intervention.

BH3 mimetics in combination with nilotinib or ponatinib represent a promising therapeutic strategy in blast phase chronic myeloid leukemia

Dysregulation of the BCL-2 family is implicated in protecting chronic myeloid leukemia (CML) cells from intracellular damage and BCR::ABL1-inhibition with tyrosine kinase inhibitors (TKIs) and may be a viable therapeutic target in blast phase (BP-)CML, for which treatment options are limited. BH3 mimetics, a class of small molecule inhibitors with high-specificity against the prosurvival members of the BCL-2 family, have displayed clinical promise in the treatment of chronic lymphocytic and acute myeloid leukemia as single agents and in combination with standard-of-care therapies. Here we present the first comparison of inhibition of BCL-2 prosurvival proteins BCL-2, BCL-xL and MCL-1 in combination with a second or third generation TKI, crucially with comparisons drawn between myeloid and lymphoid BP-CML samples. Co-treatment of four BP-CML cell lines with the TKIs nilotinib or ponatinib and either BCL-2 (venetoclax), MCL-1 (S63845) or BCL-xL (A-1331852) inhibitors resulted in a synergistic reduction in cell viability and increase in phosphatidylserine (PS) presentation. Nilotinib with BH3 mimetic combinations in myeloid BP-CML patient samples triggered increased induction of apoptosis over nilotinib alone, and a reduction in colony-forming capacity and CD34⁺ fraction, while this was not the case for lymphoid BP-CML samples tested. While some heterogeneity in apoptotic response was observed between cell lines and BP-CML patient samples, the combination of BCL-xL and BCR::ABL1 inhibition was consistently effective in inducing substantial apoptosis. Further, while BH3 mimetics showed little efficacy as single agents, dual-inhibition of BCL-2 prosurvival proteins dramatically induced apoptosis in all cell lines tested and in myeloid BP-CML patient samples compared to healthy donor samples. Gene expression and protein level analysis suggests a protective upregulation of alternative BCL-2 prosurvival proteins in response to BH3 mimetic single-treatment in BP-CML. Our results suggest that BH3 mimetics represent an interesting avenue for further exploration in myeloid BP-CML, for which alternative treatment options are desperately sought.

A case of chronic myelogenous leukemia with the T315I mutation who progressed to myeloid blast phase and was successfully treated with asciminib

Patients with chronic myelogenous leukemia (CML) harboring the T315I mutation who progress to blast phase CML while on ponatinib may be successfully treated with asciminib monotherapy following induction therapy with cytotoxic chemotherapy.

CML patients with the T315I mutation who progress to blast phase on ponatinib represent a challenging clinical scenario. Asciminib has shown efficacy in chronic phase CML patients with the T315I mutation. Asciminib should be considered for CML patients with the T315I mutation who progress to blast phase while on ponatinib.

Prognostic impact of ASXL1 mutations in chronic phase chronic myeloid leukemia

While the clinical impact of mutations in the ABL1 gene on response to therapy in chronic phase chronic myeloid leukemia (CP-CML) is well established, less is known about how other mutations affect prognosis. In a retrospective analysis, we identified 115 patients with CML (71 chronic, 15 accelerated and 29 blast phase) where targeted next-generation sequencing of genes recurrently mutated in myeloid leukemias was performed. ASXL1 was the most frequently mutated gene in the chronic (14%) and accelerated phase (40%) CML patients, whereas RUNX1 (20%) was the most common mutation in blast phase. Compared with wild-type ASXL1, CP-CML with mutant ASXL1 was associated with worse event-free survival (EFS) (median of 32.8 vs 88.3 months; P = 0.002) and failure-free survival (median of 13.8 vs 57.8 months; P = 0.04). In a multivariate analysis, ASXL1 mutation was the only independent risk factor associated with worse EFS in chronic phase CML with a hazard ratio of 4.25 (95% CI 1.59–11.35, P = 0.004). In conclusion, mutations in ASXL1 are associated with worse outcomes when detected in chronic phase CML.

Chronic Myeloid Leukemia: 2022 Update on Diagnosis, Therapy and Monitoring

DISEASE OVERVIEW

Chronic Myeloid Leukemia (CML) is a myeloproliferative neoplasm with an incidence of 1-2 cases per 100,000 adults. It accounts for approximately 15% of newly diagnosed cases of leukemia in adults DIAGNOSIS: CML is characterized by a balanced genetic translocation, t (9;22) (q34;q11.2), involving a fusion of the Abelson gene (ABL1) from chromosome 9q34 with the breakpoint cluster region (BCR) gene on chromosome 22q11.2. This rearrangement is known as the Philadelphia chromosome. The molecular consequence of this translocation is the generation of a BCR::ABL1 fusion oncogene, which in turn translates into a BCR::ABL1 oncoprotein.

FRONTLINE THERAPY

Four tyrosine kinase inhibitors (TKIs), imatinib, dasatinib, bosutinib, and nilotinib are approved by the United States Food and Drug Administration for first-line treatment of newly diagnosed CML in chronic phase (CML-CP). Clinical trials with second generation TKIs reported significantly deeper and faster responses but had no impact on survival prolongation, likely because of the availability of effective TKIs salvage therapies for patients who have a cytogenetic relapse with frontline TKI therapy.

SALVAGE THERAPY

For CML post failure on frontline therapy, second-line options include second and third generation TKIs. Although potent and selective, these TKIs exhibit unique pharmacological profiles and response patterns relative to different patient and disease characteristics, such as patients' comorbidities, disease stage, and BCR::ABL1 mutational status. Patients who develop the T315I "gatekeeper" mutation display resistance to all currently available TKIs except ponatinib, asciminib, and olverembatinib. Allogeneic stem cell transplantation remains an important therapeutic option for patients with CML-CP and failure (due to resistance) of at least 2 TKIs, and for all patients in advanced phase disease. Older patients who have a cytogenetic relapse post failure on all TKIs can maintain long-term survival if they continue a daily most effective/least toxic TKI, with or without the addition of non-TKI anti-CML agents (hydroxyurea, omacetaxine, azacitidine, decitabine, cytarabine, busulfan, others). This article is protected by copyright. All rights reserved.

Chromosomal Instability in Chronic Myeloid Leukemia: Mechanistic Insights and Effects

The most recent two decades have seen tremendous progress in the understanding and treatment of chronic myeloid leukemia, a disease defined by the characteristic Philadelphia chromosome and the ensuing BCR::ABL fusion protein. However, the biology of the disease extends beyond the Philadelphia chromosome into a nebulous arena of chromosomal and genetic instability, which makes it a genetically heterogeneous disease. The BCR::ABL oncoprotein creates a fertile backdrop for oxidative damage to the DNA, along with impairment of genetic surveillance and the favoring of imprecise error-prone DNA repair pathways. These factors lead to growing chromosomal instability, manifested as additional chromosomal abnormalities along with other genetic aberrations. This worsens with disease progression to accelerated and blast phase, and modulates responses to tyrosine kinase inhibitors. Treatment options that target the genetic aberrations that mitigate chromosome instability might be a potential area for research in patients with advanced phase CML.

Management of chronic myeloid leukemia in myeloid blastic phase with novel therapies: a systematic literature review

INTRODUCTION

Chronic myeloid leukemia at myeloid blastic phase (CML-MBP) is a rapidly lethal illness, and its prognosis is dismal with standard therapy. As the clinical and histological characteristics of CML-MBP closely resemble acute myeloid leukemia (AML), the management of these two entities has historically gone hand in hand. The remarkable success of tyrosine kinase inhibitors (TKI) for chronic phase CML significantly reduced the incidence of CML-MBP.

AREA COVERED

We performed a systematic literature review to aggregate the clinical data of CML-MBP patients who have been treated with the new drugs approved for use in AML, including decitabine, azacytidine, venetoclax, omecetaxine, glasdegib, gemtuzumab, IDH, and FLT3 inhibitors. The literature review revealed 14 articles directly contributing relevant data. We analyzed them according to the type of regimen each studied. This review will highlight selected findings from these papers.

EXPERT OPINION

Hypomethylating agent and TKI combination with or without the addition of venetoclax appear to be highly promising and have produced comparable outcomes with intensive chemotherapy and TKI combinations. Current evidence is insufficient to reach conclusions prompting dedicated research to improve the care of patients with CML-MBP.

RNA-Based Targeted Gene Sequencing Improves the Diagnostic Yield of Mutant Detection in Chronic Myeloid Leukemia

Mutation detection is increasingly used for the management of hematological malignancies. Prior whole transcriptome and whole exome sequencing studies using total RNA and DNA identified diverse mutation types in cancer-related genes associated with treatment failure in patients with chronic myeloid leukemia. Variants included single-nucleotide variants and small insertions/deletions, plus fusion transcripts and partial or whole gene deletions. The hypothesis that all of these mutation types could be detected by a single cost-effective hybridization capture next-generation sequencing method using total RNA was assessed. A method was developed that targeted 130 genes relevant for myeloid and lymphoid leukemia. Retrospective samples with 121 precharacterized variants were tested using total RNA and/or DNA. Concordance of detection of precharacterized variants using RNA or DNA was 96%, whereas the enhanced sensitivity identified additional variants. Comparison between 24 matched DNA and RNA samples demonstrated 95.3% of 170 variants detectable using DNA were detected using RNA, including all but one variant predicted to activate nonsense-mediated decay. RNA identified an additional 10 variants, including fusion transcripts. Furthermore, the true effect of splice variants on RNA splicing was only evident using RNA. In conclusion, capture sequencing using total RNA alone is suitable for detecting a range of variants relevant in chronic myeloid leukemia and may be more broadly applied to other hematological malignancies where diverse variant types define risk groups.

Myeloid neoplasms and clonal hematopoiesis from the RUNX1 perspective

RUNX1 is a critical transcription factor for the emergence of definitive hematopoiesis and the precise regulation of adult hematopoiesis. Dysregulation of its regulatory network causes aberrant hematopoiesis. Recurrent genetic alterations in RUNX1, including chromosomal translocations and mutations, have been identified in both inherited and sporadic diseases. Recent genomic studies have revealed a vast mutational landscape surrounding genetic alterations in RUNX1. Accumulating pieces of evidence also indicate the leukemogenic role of wild-type RUNX1 in certain situations. Based on these efforts, part of the molecular mechanisms of disease development as a consequence of dysregulated RUNX1-regulatory networks have become increasingly evident. This review highlights the recent advances in the field of RUNX1 research and discusses the critical roles of RUNX1 in hematopoiesis and the pathobiological function of its alterations in the context of disease, particularly myeloid neoplasms, and clonal hematopoiesis.

Genomic Mechanisms Influencing Outcome in Chronic Myeloid Leukemia

Chronic myeloid leukemia (CML) represents the disease prototype of genetically based diagnosis and management. Tyrosine kinase inhibitors (TKIs), that target the causal BCR::ABL1 fusion protein, exemplify the success of molecularly based therapy. Most patients now have long-term survival; however, TKI resistance is a persistent clinical problem. TKIs are effective in the BCR::ABL1-driven chronic phase of CML but are relatively ineffective for clinically defined advanced phases. Genomic investigation of drug resistance using next-generation sequencing for CML has lagged behind other hematological malignancies. However, emerging data show that genomic abnormalities are likely associated with suboptimal response and drug resistance. This has already been supported by the presence of BCR::ABL1 kinase domain mutations in drug resistance, which led to the development of more potent TKIs. Next-generation sequencing studies are revealing additional mutations associated with resistance. In this review, we discuss the initiating chromosomal translocation that may not always be a straightforward reciprocal event between chromosomes 9 and 22 but can sometimes be accompanied by sequence deletion, inversion, and rearrangement. These events may biologically reflect a more genomically unstable disease prone to acquire mutations. We also discuss the future role of cancer-related gene mutation analysis for risk stratification in CML.

Defining Higher-Risk Chronic Myeloid Leukemia: Risk Scores, Genomic Landscape, and Prognostication

PURPOSE OF REVIEW

The chronic myeloid leukemia (CML) treatment success story is incomplete as some patients still fail therapy, leading to end-stage disease and death. Here we discuss recent research into CML incidence, the role of comorbidities on survival and detecting patients at risk of failing therapy.

RECENT FINDINGS

The incidence of CML has fallen markedly in high social-demographic index (SDI) regions of the world but there is disturbing evidence that this is not the case in low and low-middle SDI countries. Now that CML patients more frequently die from their co-morbid conditions than from CML the Adult Comorbidity Evaluation-27 score can assist in risk assessment at diagnosis. Non-adherence to therapy contributes greatly to treatment failure. A good doctor-patient relationship and social support promote good adherence, but patient age, gender, and financial burden have negative effects, suggesting avenues for intervention. Mutations in cancer-associated genes adversely affect outcome and their detection at diagnosis may guide therapeutic choice and offer non-BCR::ABL1 targeted therapies. A differential gene expression signature to assist risk detection is a highly sought-after diagnostic tool being actively researched on several fronts. Detecting patients at risk of failing therapy is being assisted by recent technological advances enabling highly sensitive genomic and expression analysis of insensitive cells. However, patient lifestyle, adherence to therapy, and comorbidities are critical risk factors that need to be addressed by interventions such as social and financial support.

Gallbladder adenocarcinomas undergo subclonal diversification and selection from precancerous lesions to metastatic tumors

We aimed to elucidate the evolutionary trajectories of gallbladder adenocarcinoma (GBAC) using multi-regional and longitudinal tumor samples. Using whole-exome sequencing data, we constructed phylogenetic trees in each patient and analyzed mutational signatures. A total of 11 patients including 2 rapid autopsy cases were enrolled. The most frequently altered gene in primary tumors was ERBB2 and TP53 (54.5%), followed by FBXW7 (27.3%). Most mutations in frequently altered genes in primary tumors were detectable in concurrent precancerous lesions (biliary intraepithelial neoplasia [BilIN]), but a substantial proportion was subclonal. Subclonal diversity was common in BilIN (n=4). However, among subclones in BilIN, a certain subclone commonly shrank in concurrent primary tumors. In addition, selected subclones underwent linear and branching evolution, maintaining subclonal diversity. Combined analysis with metastatic tumors (n=11) identified branching evolution in nine patients (81.8%). Of these, eight patients (88.9%) had a total of 11 subclones expanded at least sevenfold during metastasis. These subclones harbored putative metastasis-driving mutations in cancer-related genes such as SMAD4, ROBO1, and DICER1. In mutational signature analysis, six mutational signatures were identified: 1, 3, 7, 13, 22, and 24 (cosine similarity >0.9). Signatures 1 (age) and 13 (APOBEC) decreased during metastasis while signatures 22 (aristolochic acid) and 24 (aflatoxin) were relatively highlighted. Subclonal diversity arose early in precancerous lesions and clonal selection was a common event during malignant transformation in GBAC. However, selected cancer clones continued to evolve and thus maintained subclonal diversity in metastatic tumors.

Blast and accelerated phase CML: room for improvement

Tyrosine kinase inhibitors (TKIs) revolutionized the treatment of chronic myeloid leukemia (CML). With TKI therapy, the percentage of patients who progress to accelerated phase (AP) or blast phase (BP) CML has decreased from more than 20% to 1% to 1.5% per year. Although AP- and BP-CML occur in a minority of patients, outcomes in these patients are significantly worse compared with chronic phase CML, with decreased response rates and duration of response to TKI. Despite this, TKIs have improved outcomes in advanced phase CML, particularly in de novo AP patients, but are often inadequate for lasting remissions. The goal of initial therapy in advanced CML is a return to a chronic phase followed by consideration for bone marrow transplantation. The addition of induction chemotherapy with TKI is often necessary for achievement of a second chronic phase. Given the small population of patients with advanced CML, development of novel treatment strategies and investigational agents is challenging, although clinical trial participation is encouraged in AP and BP patients, whenever possible. We review the overall management approach to advanced CML, including TKI selection, combination therapy, consideration of transplant, and novel agents.

Molecular Pathogenesis of BCR-ABL-Negative Atypical Chronic Myeloid Leukemia

Atypical chronic myeloid leukemia is a rare disease whose pathogenesis has long been debated. It currently belongs to the group of myelodysplastic/myeloproliferative disorders. In this review, an overview on the current knowledge about diagnosis, prognosis, and genetics is presented, with a major focus on the recent molecular findings. We describe here the molecular pathogenesis of the disease, focusing on the mechanisms of action of the main mutations as well as on gene expression profiling. We also present the treatment options focusing on emerging targeted therapies.

Which Tyrosine Kinase Inhibitors Should Be Selected as the First-Line Treatment for Chronic Myelogenous Leukemia in Chronic Phase?

Simple Summary

This review discusses the optimal selection of BCR-ABL1 tyrosine kinase inhibitors (TKIs) as the first-line treatment for newly diagnosed chronic myelogenous leukemia in chronic phase (CML-CP). With the advent of TKIs, the treatment goals for CML-CP patients have changed from “simply survival” to “survival with adequate quality of life”, hence the number of CML-CP patients aiming to achieve treatment-free remission has increased, irrespective of age or comorbidities. Therefore, optimal selection of TKIs for maximizing the number of patients to achieve treatment-free remission is an important factor for consideration in future studies. To this end, we must understand the advantages and disadvantages of each TKI in terms of treatment response, disease risk at diagnosis, comorbidities, and medical expenses, and use of effective 2GTKIs based on patient background. This review provides insights into “shared decision-making” in individual cases, including the elderly population.

Abstract

With the use of tyrosine kinase inhibitors (TKIs), chronic myelogenous leukemia in chronic phase (CML-CP) has been transformed into a non-fatal chronic disease. Hence, “treatment-free remission (TFR)” has become a possible treatment goal of patients with CML-CP. Currently, four types of TKIs (imatinib, nilotinib, dasatinib, and bosutinib) are used as the first-line treatment for newly diagnosed CML-CP. However, the second-generation TKI (2GTKI), the treatment response of which is faster and deeper than that of imatinib, is not always recommended as the first-line treatment for CML-CP. Factors involved in TKI selection in the first-line treatment of CML-CP include not only patients’ medical background, but also patients’ choice regarding the desired treatment goal (survival or TFR?). Therefore, it is important that clinicians select an appropriate TKI to successfully achieve the desired treatment goal for each patient, while minimizing the development of adverse events. This review compares the pros and cons of using imatinib and 2GTKI for TKI selection as the first-line treatment for CML-CP, mainly considering treatment outcomes, medical history (i.e., desire for pregnancy, aging factor, and comorbidity), and cost. The optimal use of 2GTKIs is also discussed.

Impact of frontline treatment approach on outcomes of myeloid blast phase CML

Background

The natural course of untreated chronic myeloid leukemia (CML) is progression to an aggressive blast phase. Even in the current era of BCR-ABL1 tyrosine kinase inhibitors (TKIs), the outcomes of blast phase CML remain poor with no consensus frontline treatment approach.

Methods

We retrospectively analyzed the response rates and survival outcomes of 104 consecutive patients with myeloid blast phase CML (CML-MBP) treated from 2000 to 2019 based on 4 different frontline treatment approaches: intensive chemotherapy (IC) + TKI (n = 20), hypomethylating agent (HMA) + TKI (n = 20), TKI alone (n = 56), or IC alone (n = 8). We also evaluated the impact of TKI selection and subsequent allogeneic stem cell transplant (ASCT) on patient outcomes.

Results

Response rates were similar between patients treated with IC + TKI and HMA + TKI. Compared to treatment with TKI alone, treatment with IC/HMA + TKI resulted in a higher rate of complete remission (CR) or CR with incomplete count recovery (CRi) (57.5% vs 33.9%, p < 0.05), a higher complete cytogenetic response rate (45% vs 10.7%, p < 0.001), and more patients proceeding to ASCT (32.5% vs 10.7%, p < 0.01). With a median follow-up of 6.7 years, long-term outcomes were similar between the IC + TKI and HMA + TKI groups. Combination therapy with IC/HMA + TKI was superior to therapy with TKI alone, including when analysis was limited to those treated with a 2nd/3rd-generation TKI. When using a 2nd/3rd-generation TKI, IC/HMA + TKI led to lower 5-year cumulative incidence of relapse (CIR; 44% vs 86%, p < 0.05) and superior 5-year event-free survival (EFS; 28% vs 0%, p < 0.05) and overall survival (OS; 34% vs 8%, p = 0.23) compared to TKI alone. Among patients who received IC/HMA + TKI, EFS and OS was superior for patients who received a 2nd/3rd generation TKI compared to those who received imatinib-based therapy. In a landmark analysis, 5-year OS was higher for patients who proceeded to ASCT (58% vs 22%, p = 0.12).

Conclusions

Compared to patients treated with TKI alone for CML-MBP, treatment with IC + TKI or HMA + TKI led to improved response rates, CIR, EFS, and OS, particularly for patients who received a 2nd/3rd-generation TKI. Combination therapy with IC + TKI or HMA + TKI, rather than a TKI alone, should be considered the optimal treatment strategy for patients with CML-MBP.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13045-021-01106-1.