Myelodysplastic syndromes and acute leukemia developing after imatinib mesylate therapy for chronic myeloid leukemia

Clinical Features of Clonal Cytogenetic Abnormalities in Philadelphia-negative Cells Developed During Tyrosine Kinase Inhibitor Treatment

Most clonal cytogenetic abnormalities of Philadelphia-negative cells (CCA/Ph-) occurring during tyrosine kinase inhibitor (TKI) treatment are transient, and the development of secondary myelodysplastic syndrome (MDS)/acute myeloid leukemia (AML) is rare, but the frequency and clinical significance in Japanese patients are still unknown. We herein report four patients who developed CCA/Ph- during TKI therapy and were diagnosed with secondary MDS/AML. The duration from TKI therapy initiation to MDS/AML onset ranged from 3 to 48 months, and the survival ranged from 5 to 84 months. The occurrence of CCA/Ph- with MDS/AML may be associated with a poor prognosis, and careful follow-up is recommended for patients who receive TKI therapy.

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.

Secondary Acute Myeloid Leukemia in a Chronic Myeloid Leukemia Patient in Deep Molecular Response—An Unusual Case Report

Chronic myeloid leukemia (CML) is a clonal myeloproliferative disorder that develops from the stem cell compartment. The classical translocation (BCR-ABL1) is present in approximately 95% of CML patients. Through disease progression, clonal evolution with additional chromosomal abnormalities (ACAs) start appearing. Although relatively rare, chromosomal abnormalities can exist or develop in the Philadelphia (Ph)-negative clones, which may lead to the evolution of myelodysplastic syndrome (MDS) or acute myeloid leukemia (AML). We hereby present a case of AML which emerged from a Ph-negative clone in a patient with a history of CML who was in deep molecular response. The possible mechanisms of ACAs have been discussed.

Development of Philadelphia chromosome-negative acute myeloid leukemia with IDH2 and NPM1 mutations in a patient with chronic myeloid leukemia who showed a major molecular response to tyrosine kinase inhibitor therapy

Tyrosine kinase inhibitors (TKIs) are standard therapies for chronic myeloid leukemia (CML) that can eradicate Ph-positive leukemic cells. However, disease control is not achievable in a minority of cases, most commonly due to evolution of TKI-resistant clones. There have also been rare cases of emergence of Ph-negative clones with other cytogenetic abnormalities, and, less commonly, development of Ph-negative acute myeloid leukemia (AML), whose molecular pathogenesis is largely unknown. Here we report molecular features of a patient with Ph + CML who developed Ph-negative AML after showing a major molecular response to dasatinib. A 55-year-old man was diagnosed with CML. He achieved a complete cytogenetic response three months after dasatinib therapy but developed AML with normal karyotype 1 year later. After receiving induction and consolidation chemotherapy for AML, the patient achieved complete remission with no evidence of CML under maintenance with bosutinib. Targeted sequencing of serial bone marrow samples identified mutations in IDH2 and NPM1 in the Ph-negative AML cells, which had not been detected in CML cells. These results suggest that Ph-negative AML in this patient originated from a preleukemic population, which might have expanded during or after the successful elimination of CML clones with TKI therapy.

Case Report of acute myeloid leukemia with "WT1, ATRX, CEBPA, CSMD1, IKZF1, and LRP1B mutation and translocation between chromosome 1 and 19" developing from Philadelphia-negative chronic myeloid leukemia after TKI therapy

RATIONALE

The success of tyrosine kinase inhibitor (TKI) therapy has greatly prolonged the survival time of patients with chronic myeloid leukemia (CML), harboring the characteristic Philadelphia (Ph) chromosome. However, a fraction of patients, achieving complete cytogenetic response after TKI therapy, develop a myelodysplastic syndrome (MDS) or acute myeloid leukemia (AML) with additional clonal chromosomal abnormalities in Philadelphia-negative cells (CCA/Ph-).

PATIENT CONCERNS

A 56-year-old woman with AML, developing from Philadelphia-negative CML after TKI therapy. She showed 6 kinds of somatic variants-CEBPA, ATRX, WT1, CSMD1, IKZF1, and LRP1B mutation after diagnosed as AML.

DIAGNOSIS

The patient was diagnosed with chronic phase CML that developed to AML after achieving durable complete cytogenetic response (CCR) and major molecular response (MMR).

INTERVENTIONS

The patient was treated with TKI therapy at the period of CML. When diagnosed with AML, she received induction chemotherapy regimens, consolidation therapy, and allogeneic hematopoietic stem cell transplantation subsequently.

OUTCOMES

The patient has been CCR and MMR for nearly 4 years, and has achieved complete remission after intervention related to AML. She is now preparing for allogeneic hematopoietic stem cell transplantation.

LESSONS

These rare occurrences highlight the importance of exploring the relevant pathogenesis of AML developing from CML after TKI therapy. In addition to monitoring molecular changes in the course of CML, cytogenetic analysis, or next-generation sequencing of CML patients should be performed.

Trisomy 8 in acute myeloid leukemia

Introduction: Trisomy 8 is one of the most common cytogenetic alterations in acute myeloid leukemia (AML), with a frequency between 10% and 15%.Areas covered: The authors summarize the latest research regarding biological, translational and clinical aspects of trisomy 8 in AML.Expert opinion: Trisomy 8 can be found together with other karyotypes, although it also occurs as a sole aberration. The last decade's research has brought attention to molecular genetic alterations as strong contributors of leukemogenesis. AML with trisomy 8 seems to be associated with mutations in DNA methylation genes, spliceosome complex genes, and myeloid transcription factor genes, and these alterations probably have stronger implication for leukemic pathogenesis, treatment and hence prognosis, than the existence of trisomy 8 itself. Especially mutations in the RUNX1 and ASXL1 genes occur in high frequencies, and search for such mutations should be mandatory part of the diagnostic workup. AML with trisomy 8 is classified as intermediate-risk AML after recent European Leukemia Net (ELN) classification, and hence allogenic hematopoietic stem cell transplantation (Allo-HSCT) should be consider as consolidation therapy for this patient group.Trisomy 8 is frequently occurring in AML, although future molecular genetic workup should be performed, to optimize the diagnosis and treatment of these patients.

[Philadelphia chromosome-negative myeloid neoplasms in patients with Philadelphia chromosome-positive chronic myeloid leukemia during tyrosine kinase inhibtor-therapy]

Objective: To compare the clinical features between the 2 cohorts developing myelodysplastic syndrome or acute myeIogenous Ieukemia in Philadelphia chromosome-negative cells (Ph(-) MDS/AML) and maintaining disease stable in the patients with Philadelphia chromosome-positive chronic myeloid Ieukemia (Ph(+) CML) who had clonal chromosomal abnormalities in Philadelphia chromosome-negative metaphases (CCA/Ph(-)) during tyrosine kinase inhibtor (TKI) - therapy. Methods: We retrospectively analyzed Ph(+) CML patients who developed CCA/Ph(-) during TKI-therapy from May 2001 to December 2017. Results: Data of CCA/Ph(-) 63 patients, including 7 progressing to Ph(-) MDS/AML and 56 remaining disease stable were collected. Compared with those with stable disease, patients with Ph(-)MDS/AML had lower hemoglobin (P=0.007) and platelet (P=0.006) counts, and higher proportion of peripheral blasts (P<0.001) when the first time CCA/Ph(-) was detected, and more mosonomy 7 abnormality (5/7, 71.4%) when MDS or AML was diagnosed; meanwhile, trisomy 8 (32/56, 57.1%) was more common in those with stable disease. Outcome of the patients with Ph(-) MDS/AML were poor. However, most of those with CCA/Ph(-) and stable disease had optimal response on TKI-therapy. Conclusions: A few patients with Ph(+) CML developed CCA/Ph(-) during TKI-therapy, most of them had stable disease, but very few patients developed Ph(-) MDS/AML with more common occurrence of monosomy 7 or unknown cytopenia. Our data suggested the significance of monitoring of peripheral blood smear, bone marrow morphology and cytogenetic analysis once monosomy 7 or unknown cytopenia occurred.

Chronic Myeloid Leukemia: Beyond BCR-ABL1

PURPOSE OF REVIEW

In this review, we emphasize up-to-date practical cytogenetic and molecular aspects of chronic myeloid leukemia (CML) and summarize current knowledge on tyrosine kinase inhibitor (TKI) resistance and treatment response monitoring of CML.

RECENT FINDINGS

The introduction of TKIs has changed the natural course of CML and markedly improved patient survival. Over the past decades, many research efforts were devoted to elucidating the leukemogenic mechanisms of BCR-ABL1 and developing novel TKIs. More recent studies have attempted to answer new questions that have emerged in the TKI era, such as the cytogenetic and molecular bases of treatment failure and disease progression, the clinical impact of genetic aberrations in Philadelphia chromosome (Ph)-positive and Ph-negative cells, and the biological significance of Ph secondarily acquired during therapy of other hematological neoplasms. Recent progresses in the understanding of the cytogenetic and molecular mechanisms underlying therapeutic failure and disease progression have improved the risk stratification of CML and will be helpful in the design of novel therapeutic strategies.

Bone marrow fibrosis associated with long-term imatinib therapy: resolution after switching to a second-generation TKI

Bone marrow fibrosis may be a late reversible toxicity of high-dose imatinib therapy in chronic myeloid leukemia.

Ethnic Differences in Hematologic Toxicity from Imatinib in Patients with Gastrointestinal Stromal Cell Tumor (GIST): Coincidence or a Real Phenomenon

Objectives:

There is a wide variability in the pharmacokinetics, pharmacodynamics and tolerance of anticancer drugs based on ethnicity. GIST is a rare cancer, (~1% of GI cancers). Imatinib is used in the neo-adjuvant, adjuvant and metastatic setting. The purpose of this study was to report the difference in hematologic toxicities to imatinib among different ethnicities when treated for GIST either in the adjuvant or metastatic setting.

Methods:

We performed a retrospective study to collect data on patients with GIST (in any stage), who were on imatinib and presenting with grade 2 or more anemia, neutropenia and/or thrombocytopenia from July 1, 2005 to January 31, 2018. The degree of cytopenia was graded as per National Cancer Institute Common Toxicity criteria; version 4.0. We collected included age, gender, ethnicity, pathology, adverse effects-hematologic and non-hematologic, management of toxicities including dose modifications and administration of pegfilgrastim.

Results:

Among 57 patients (median age 61 years, M: F=41:16 (F); ethnicities: White 65%, African-American (AA 19%, Asian 12% and Hispanic 4%), neutropenia (Grade 3 & 4) was seen in 6 patients (10%): 5 AA and 1 Asian. 45% of all AA patients developed neutropenia. Median absolute neutrophil count (ANC) nadir was 700/μL, median duration on drug prior to onset of neutropenia was 4.5 weeks and median duration of neutropenia was 4 weeks. One patient developed febrile neutropenia. Dose interruptions were needed in 3, dose-reductions in all patients, and 3 patients required pegfilgrastim. One patient had to discontinue imatinib, while one patient was escalated back to 400mg daily dose.

Conclusion:

This is the first study to examine ethnic variations in myelosuppression following imatinib in patients with GIST.

Poor prognosis of chromosome 7 clonal aberrations in Philadelphia-negative metaphases and relevance of potential underlying myelodysplastic features in chronic myeloid leukemia

Clonal chromosome abnormalities in Philadelphia-negative cells could concern chronic myeloid leukemia patients treated by tyrosine kinase inhibitors. The European LeukemiaNet distinguishes -7/del(7q) abnormalities as a “warning”. However, the impact of clonal chromosome abnormalities, and specifically those of -7/del(7q), in Philadelphia-negative cells on clinical outcomes is unclear and based on case-reports showing morphological dysplasia and increased risk of acute myeloid leukemia, suggesting the coexistence of chronic myeloid leukemia and high-risk myelodysplastic syndrome. The aim of this study was to determine whether the impact of -7/del(7q) clonal chromosome abnormalities in Philadelphia-negative cells on the clinical outcome is different from that of other types of abnormalities, and we argue for an underlying associated high-risk myelodysplastic syndrome. Among 102 chronic myeloid leukemia patients with clonal chromosome abnormalities in Philadelphia-negative cells with more than a median of 6 years of follow up, patients with -7/del(7q) more frequently had signs of dysplasia, a lower cumulative incidence of deep molecular response and often needed further treatment lines, with the consequent impact on event-free and progression-free survival. Morphological features of dysplasia are associated with myelodysplastic syndrome/acute myeloid leukemia mutations and compromise the optimal response to tyrosine kinase inhibitors, irrespectively of the type of clonal chromosome abnormalities in Philadelphia-negative cells. However, mutation patterns determined by next-generation sequencing could not clearly explain the underlying high-risk disease. We hereby confirm the pejorative prognostic value of -7/del(7q) clonal chromosome abnormalities in Philadelphia-negative cells and suggest that myelodysplastic features constitute a warning signal that response to tyrosine kinase inhibitors may be less than optimal.

Characterisation of clonal Philadelphia-negative cytogenetic abnormalities in a large cohort of chronic myeloid leukaemia

BACKGROUND

Clonal Philadelphia (Ph)-negative cytogenetic abnormalities (CPCA) have been reported in chronic myeloid leukaemia (CML) patients treated with either interferon or tyrosine kinase inhibitor (TKI). However, the incidences and types of these cytogenetic abnormalities after treatment vary due to the limited populations enroled.

METHODS

We analysed the frequency and types of CPCA in a cohort of 607 CML patients in the chronic phase after TKI treatment. We also followed up these CPCA with a median of 31.8 months (range from 11 to 63 months) from diagnosis and investigated their effects on disease progression.

RESULTS

We found 18 out of 607 CML patients had cytogenetic abnormality in the Ph-negative cells with an incidence of 3%. In total, six types of chromosomal abnormalities have been identified in these 18 patients with the majority of them aneuploidy abnormalities, especially the trisomy 8. Four of 18 patients (22.2%) were noted to have several abnormalities in the Ph-negative cells. Furthermore, follow-up studies of these CPCA showed that they could be either persistent or transient (15 vs 3 patients), and may not affect disease progression since none of them developed transformed myelodysplasia or transformed acute myeloid leukaemia.

CONCLUSION

Three percent of CML patients in the chronic phase were observed to have CPCA during TKI treatment. Our results suggest that the detection of CPCA in CML may not predict disease progression.

Integrated computational biology analysis to evaluate target genes for chronic myelogenous leukemia

Although hundreds of genes have been linked to chronic myelogenous leukemia (CML), many of the results lack reproducibility. In the present study, data across multiple modalities were integrated to evaluate 579 CML candidate genes, including literature‑based CML‑gene relation data, Gene Expression Omnibus RNA expression data and pathway‑based gene‑gene interaction data. The expression data included samples from 76 patients with CML and 73 healthy controls. For each target gene, four metrics were proposed and tested with case/control classification. The effectiveness of the four metrics presented was demonstrated by the high classification accuracy (94.63%; P<2x10‑4). Cross metric analysis suggested nine top candidate genes for CML: Epidermal growth factor receptor, tumor protein p53, catenin β 1, janus kinase 2, tumor necrosis factor, abelson murine leukemia viral oncogene homolog 1, vascular endothelial growth factor A, B‑cell lymphoma 2 and proto‑oncogene tyrosine‑protein kinase. In addition, 145 CML candidate pathways enriched with 485 out of 579 genes were identified (P<8.2x10‑11; q=0.005). In conclusion, weighted genetic networks generated using computational biology may be complementary to biological experiments for the evaluation of known or novel CML target genes.

Dasatinib and Azacitidine Followed by Haploidentical Stem Cell Transplant for Chronic Myeloid Leukemia with Evolving Myelodysplasia: A Case Report and Review of Treatment Options

BACKGROUND CML presenting with a variant Philadelphia translocation, atypical BCR-ABL transcript, additional chromosomal aberrations, and evolving MDS is uncommon and therapeutically challenging. The prognostic significance of these genetic findings is uncertain, even as singular aberrations, with nearly no data on management and outcome when they coexist. MDS evolving during the course of CML may be either treatment-associated or an independently coexisting disease, and is generally considered to have an inferior prognosis. Tyrosine kinase inhibitors (TKI) directed against BCR-ABL are the mainstay of treatment for CML, whereas treatment modalities that may be utilized for MDS and CML include allogeneic stem cell transplant and - at least conceptually - hypomethylating agents. CASE REPORT Here, we describe the clinical course of such a patient, demonstrating that long-term combined treatment with dasatinib and azacitidine for coexisting CML and MDS is feasible and well tolerated, and may be capable of slowing disease progression. This combination therapy had no deleterious effect on subsequent potentially curative haploidentical bone marrow transplantation. CONCLUSIONS The different prognostic implications of this unusual case and new therapeutic options in CML are discussed, together with a review of the current literature on CML presenting with different types of genomic aberrations and the coincident development of MDS. Additionally, this case gives an example of long-term combined treatment of tyrosine kinase inhibitors and hypomethylating agents, which could be pioneering in CML treatment.

Diagnostic and prognostic cytogenetics of chronic myeloid leukaemia: an update

INTRODUCTION

Despite the advent of molecular assessment, banding cytogenetics and fluorescence in situ hybridization (FISH) still have a significant role in diagnostic and prognostic approaches to chronic myeloid leukaemia (CML). Area covered: At diagnosis and during treatment with tyrosine kinase inhibitors (TKIs), cytogenetics is used to detect the Philadelphia chromosome, with its typical translocation t(9;22)(q34;q11.2), and any additional or other chromosomal aberrations (ACAs and OCAs) that may arise in 5-10% of cases, the latter associated to transformation of the disease in blast phases. In this review, the potential role of banding cytogenetics and FISH is discussed through a review of published papers on the prognostic impact of these tools in CML treatment and monitoring. Expert commentary: Cytogenetic techniques, including banding cytogenetics and FISH, continue to maintain a crucial role in CML monitoring. At diagnosis and after 3 months of therapy, banding cytogenetics will continue to be an essential test to perform, but it will become redundant after the achievement of a major molecular response (MMR) assessed with molecular techniques. FISH analysis maintains its usefulness in monitoring the response to TKIs only in special situations.

Clonal chromosomal abnormalities appearing in Philadelphia chromosome-negative metaphases during CML treatment

Clonal chromosomal abnormalities in Philadelphia chromosome-negative (CCA/Ph^-) metaphases emerge as patients with chronic phase chronic myeloid leukemia (CP-CML) are treated with tyrosine kinase inhibitors (TKIs). We assessed the characteristics and prognostic impact of 598 patients with CP-CML treated on clinical trials with various TKIs. CCA/Ph^- occurred in 58 patients (10%); the most common were -Y in 25 (43%) and trisomy 8 in 7 patients (12%). Response to TKI therapy was similar for patients with CCA/Ph^- and those without additional chromosomal abnormalities (ACAs). We further categorized CCA/Ph^- into those in which -Y was the only clonal abnormality, and all others. We found that patients with non -Y CCA/Ph^- had worse failure-free survival (FFS), event-free survival (EFS), transformation-free survival (TFS), and overall survival (OS) compared with those without ACAs with the following 5-year rates: FFS (52% vs 70%, P = .02), EFS (68% vs 86%, P = .02), TFS (76% vs 94%, P < .01), and OS (79% vs 94%, P = .03). In a multivariate analysis, non -Y CCA/Ph^- increased the risk of transformation or death when baseline characteristics were considered with a hazard ratio of 2.81 (95% confidence interval, 1.15-6.89; P = .02). However, this prognostic impact was not statistically significant when achieving BCR-ABL <10% at 3 months was included in the analysis. In conclusion, non -Y CCA/Ph^- are associated with decreased survival when emerging in patients with chronic-phase CML across various TKIs. This trial was registered at www.clinicaltrials.gov as #NCT00048672, #NCT00038649, and #NCT00050531 (imatinib); #NCT00254423 (dasatinib); #NCT00129740 (nilotinib); and NCT01570868 (ponatinib).

Clonal chromosomal aberrations in Philadelphia negative cells such as monosomy 7 and trisomy 8 may persist for years with no impact on the long term outcome in patients with chronic myeloid leukemia

The appearance of clonal chromosomal aberrations in Philadelphia negative cells (CCA/Ph-) during the treatment of chronic myeloid leukemia (CML) was recently confirmed. Importance of these findings has not been clearly defined. We present data on the time of appearance, persistence, size of the CCA/Ph- clone in terms of drugs used and hematological, cytogenetic and molecular response rates. The focus was on the peripheral blood cytopenias and myelodysplastic changes in the bone marrow microscopic evaluation. In 5 out of 155 (3,2%) CML patients, the persistent presence (up to nine years) of CCA/Ph- was found (monosomy 7 and trisomy 8 in unrelated clones in two patients treated with tyrosine kinase inhibitors; trisomy 8 in two patients on imatinib; trisomy 21 in one patient on interferon alfa treatment). Aberrations were present in median 24% Ph- cells in 3-15 subsequent analyses at different cytogenetic and molecular response time points. No evident myelodysplastic changes nor transformation to MDS/AML occurred in patients with CCA/Ph-. All the patients achieved major molecular response (MMR). It seems that CCA/Ph- presence does not affect the long term outcome in patients with chronic myeloid leukemia. Further complex monitoring of the CML patients with CCA/Ph- is still needed.

Transient monosomy 7 in a chronic myelogenous leukemia patient during nilotinib therapy: a case report

Tyrosine kinase inhibitor treated chronic myelogenous leukemia patients with monosomy 7 arising in Philadelphia chromosome negative (Ph−) cells tend to evolve into MDS/AML. However, monosomy 7 in Ph− cells can be a transient finding, and it is not an absolute indication of the emergence of a new myeloid malignancy.

Successful Bosutinib Experience in an Elderly Acute Lymphoblastic Leukemia Patient with Suspected Central Nervous System Involvement Transformed from Chronic Myeloid Leukemia

Managing the blast phase in chronic myeloid leukemia (CML) is challenging because limited data are available for elderly patients. The involvement of the central nervous system (CNS) increases the risk of a poor prognosis. Here, we present an elderly blast phase CML patient with suspected CNS involvement who was successfully treated with bosutinib.

Killing two birds with one stone: a case of GIST and supervening CML

A 50-year-old patient who presented with abdominal pain was found to have a suspicious 8 × 6 × 9 cm mass in the left upper abdomen on imaging. A complete surgical resection of the mass was performed subsequently and pathology revealed a gastrointestinal stromal tumour. The patient was started on adjuvant Imatinib following the resection. Four years later, reimaging demonstrated no evidence of disease and adjuvant therapy was discontinued. Nine months following discontinuation of Imatinib, routine blood work revealed marked leucocytosis. Further work up including peripheral smear and bone marrow biopsy showed findings consistent with chronic myelogenous leucaemia. Imatinib was restarted and the patient's white cell counts returned to normal range within a month.

Diagnosis and Treatment of Chronic Myeloid Leukemia in 2015

Few neoplastic diseases have undergone a transformation in a relatively short period like chronic myeloid leukemia (CML) has in the last few years. In 1960, CML was the first cancer in which a unique chromosomal abnormality was identified and a pathophysiologic correlation suggested. Landmark work followed, recognizing the underlying translocation between chromosomes 9 and 22 that gave rise to this abnormality and, shortly afterward, the specific genes involved and the pathophysiologic implications of this novel rearrangement. Fast forward a few years and this knowledge has given us the most remarkable example of a specific therapy that targets the dysregulated kinase activity represented by this molecular change. The broad use of tyrosine kinase inhibitors has resulted in an improvement in the overall survival to the point where the life expectancy of patients today is nearly equal to that of the general population. Still, there are challenges and unanswered questions that define the reasons why the progress still escapes many patients, and the details that separate patients from ultimate cure. In this article, we review our current understanding of CML in 2015, present recommendations for optimal management, and discuss the unanswered questions and what could be done to answer them in the near future.

Chronic myeloid leukemia: Relevance of cytogenetic and molecular assays

Chronic myeloid leukemia (CML) is the prototype cytogenetic malignancy. Even before the development of basic G- and R-banding techniques, CML was found to be associated with a persistent chromosomal abnormality, the Philadelphia (Ph) chromosome. Banding technology later showed the marker chromosome to be a translocation between the breakpoint cluster region (BCR) on chromosome 22q11.2 and the Abelson proto-oncogene (ABL) on chromosome 9q34. Further advances in cytogenetic and molecular biology have also contributed to the understanding, diagnosis, and treatment of CML. Fluorescent in situ hybridization (FISH) has revealed cryptic translocations in most cases of Ph-negative CML. Additional rare chromosomal variant translocations have been discovered as well. The understanding of cytogenetic and molecular physiopathology of CML has led to the use of tyrosine kinase inhibitors as treatment for this disease with spectacular success. Over the 40 years since being identified as the first cytogenetic disease, CML has become the greatest success in translating the basic science of oncology into the treatment of patients with cancer. In this review we will not only summarize the biology of CML, recent progress in the delineation of mechanisms and treatment strategies, but also we will discuss the laboratory tools used for diagnosing CML, for monitoring during treatment and for revealing point mutations and additional chromosomal abnormalities. In doing so, we will describe in detail our individual research on CML, identifying why and how these tests were performed to help to explain CML subgroups and clinical significance of additional chromosomal abnormalities.

Acute Myeloid Leukemia and Other Types of Disease Progression in Myeloproliferative Neoplasms

OBJECTIVES

This session of the Society for Hematopathology/European Association for Haematopathology workshop focused on disease progression in myeloproliferative neoplasms (MPNs).

METHODS

The session included typical and unusual presentations of chronic myelogenous leukemia (CML), BCR-ABL1 positive; Philadelphia chromosome-negative (Ph-neg) MPNs; and mastocytosis.

RESULTS

Cases of CML illustrated various manifestations of progression, with emphasis on criteria defining stages of the disease. Issues were discussed related to the patterns of recurrence in patients receiving tyrosine kinase inhibitor therapy, including leukemic transformation occurring in a Ph-neg clone. Ph-neg MPN cases highlighted diagnostic approaches used to establish accelerated and blast phases, including cases with significant myelofibrosis and when an adequate bone marrow aspirate smear is not available. The session also included rare cases of aggressive mastocytosis.

CONCLUSIONS

There was agreement that a definitive diagnosis can be challenging in the absence of documented review of prior diagnostic material and clinical history.

Ph-negative isolated myeloid sarcoma with NPM1 gene mutation in adolescent with Ph-positive chronic myeloid leukemia in remission after treatment with allogeneic bone marrow transplantation and imatinib mesylate

Few patients in remission of Ph-positive chronic myelogenous leukemia (CML) develop Ph-negative MDS/AML, usually with clonal cytogenetic abnormalities. Isolated Ph-negative myeloid sarcoma (MS) is presented here as a form of such disorder, different from Ph-positive MS establishing CML relapse in blastic phase. We describe 11-year-old male who developed Ph-negative isolated MS with NPM1 mutation, remaining in complete molecular remission of Ph-positive chronic myeloid leukemia treated with allo-HSCT in first chronic phase and with imatinib and donor lymphocyte infusion in molecular relapse. The possible mechanisms of the tumor formation are reviewed with stress on importance of comprehensive molecular/cytogenetic evaluations.

Chromosomal rearrangement involving 11q23 locus in chronic myelogenous leukemia: a rare phenomenon frequently associated with disease progression and poor prognosis

Background

Progression of chronic myelogenous leukemia (CML) is frequently accompanied by cytogenetic evolution, commonly unbalanced chromosomal changes, such as an extra copy of Philadelphia chromosome (Ph), +8, and i(17)(q10). Balanced chromosomal translocations typically found in de novo acute myeloid leukemia occur occasionally in CML, such as inv(3)/t(3;3), t(8;21), t(15;17), and inv(16). Translocations involving the 11q23, a relatively common genetic abnormality in acute leukemia, have been seldom reported in CML. In this study, we explored the prevalence and prognostic role of 11q23 in CML.

Methods

We searched our pathology archives for CML cases diagnosed in our institution from 1998 to present. Cases with 11q23 rearrangements were retrieved. The corresponding clinicopathological data were reviewed.

Results

A total of 2,012 cases of CML with available karyotypes were identified. Ten (0.5%) CML cases had 11q23 rearrangement in Ph-positive cells, including 4 cases of t(9;11), 2 cases of t(11;19), and 1 case each of t(2;11), t(4;11), t(6;11), and t(4;9;11). Eight cases (80%) had other concurrent chromosomal abnormalities. There were 6 men and 4 women with a median age of 50 years (range, 21–70 years) at time of initial diagnosis of CML. 11q23 rearrangement occurred after a median period of 12.5 months (range, 0–172 months): 1 patient in chronic phase, 2 in accelerated phase, and 7 in blast phase. Eight of ten patients died after a median follow-up of 16.5 months (range, 8–186 months) following the initial diagnosis of CML, and a median of 6.7 months (range, 0.8–16.6 months) after the emergence of 11q23 rearrangement. The remaining two patients had complete remission at the last follow-up, 50.2 and 6.9 months, respectively. In addition, we also identified a case with 11q23/t(11;17) in Ph-negative cells in a patient with a history of CML. MLL involvement was tested by fluorescence in situ hybridization in 10 cases, and 7 cases (70%) were positive.

Conclusions

In summary, chromosomal rearrangements involving 11q23 are rare in CML, frequently occurring in blast phase, and are often associated with other cytogenetic abnormalities. These patients had a low response rate to tyrosine kinase inhibitors and a poor prognosis.

Philadelphia chromosome-negative acute myeloid leukemia with 11q23/MLL translocation in a patient with chronic myelogenous leukemia

Although defined by the presence of t(9;22), chronic myelogenous leukemia (CML) can have other concurrent additional cytogenetic changes, especially during disease progression. Additional chromosomal changes (ACAs) in CML often occur in Philadelphia chromosome (Ph)-positive cells and are associated with disease acceleration and treatment resistance. Occasionally chromosomal changes occur in Ph-negative cells and this phenomenon is often transient and does not correlate with disease progression. Very rarely myelodysplastic syndrome or acute leukemia can develop in Ph-negative cells. In this study, we report an unusual case of acute myeloid leukemia (AML) with 11q23/MLL translocation emerging from Ph-negative cells in a patient with CML.

Mosaike in der Tumorzytogenetik

Eine Tumorerkrankung stellt, bezogen auf den Gesamtorganismus, per definitionem ein Mosaik dar. Zusätzlich sind die meisten Tumoren, für sich betrachtet, Mosaike. Dieser Mosaikstatus wird üblicherweise als intratumorale Heterogenität bezeichnet und ist ein wesentlicher Faktor, der sowohl Relevanz für die Diagnostik als auch für die therapeutischen Strategien hat. Um die genetischen Veränderungen eines Tumors analysieren zu können, muss im Rahmen der Diagnostik sichergestellt werden, dass eine ausreichende Anzahl an Tumorzellen ausgewertet werden kann und nicht lediglich das normale Gewebe betrachtet wird. Dieses wird in der Diagnostik bei den verschiedenen Neoplasien mit unterschiedlichen Vorgehensweisen in Abhängigkeit von den verwendeten diagnostischen Methoden und der Art der Neoplasie erreicht. Zur Anwendung kommen Methoden, die die malignen Zellen anreichern und diese gezielt zur Proliferation stimulieren, oder die Methode wird mit einer ausreichenden Sensitivität durchführt, um auch kleine Klone erfassen zu können.

Molecular-defined clonal evolution in patients with chronic myeloid leukemia independent of the BCR-ABL status

To study clonal evolution in chronic myeloid leukemia (CML), we searched for BCR-ABL-independent gene mutations in both Philadelphia chromosome (Ph)-negative and Ph-positive clones in 29 chronic-phase CML patients by targeted deep sequencing of 25 genes frequently mutated in myeloid disorders. Ph-negative clones were analyzed in 14 patients who developed clonal cytogenetic abnormalities in Ph-negative cells during treatment with tyrosine kinase inhibitors (TKI). Mutations were detected in 6/14 patients (43%) affecting the genes DNMT3A, EZH2, RUNX1, TET2, TP53, U2AF1 and ZRSR2. In two patients, the mutations were also found in corresponding Ph-positive diagnostic samples. To further investigate Ph-positive clones, 15 randomly selected CML patients at diagnosis were analyzed. Somatic mutations additional to BCR-ABL were found in 5/15 patients (33%) affecting ASXL1, DNMT3A, RUNX1 and TET2. Analysis of individual hematopoietic colonies at diagnosis revealed that most mutations were part of the Ph-positive clone. In contrast, deep sequencing of subsequent samples during TKI treatment revealed one DNMT3A mutation in Ph-negative cells that was also present in Ph-positive cells at diagnosis, implying that the mutation preceded the BCR-ABL rearrangement. In summary, BCR-ABL-independent gene mutations were frequently found in Ph-negative and Ph-positive clones of CML patients and may be considered as important cofactors in the clonal evolution of CML.

BMI1 reprogrammes histone acetylation and enhances c-fos pathway via directly binding to Zmym3 in malignant myeloid progression

The polycomb group BMI1 is proved to be crucial in malignant myeloid progression. However, the underlying mechanism of the action of BMI1 in myeloid malignant progression was not well characterized. In this study, we found that the patients of both myelodysplastic syndromes and chronic myeloid leukaemia with BMI1 overexpression had a higher risk in malignant myeloid progression. In vitro gene transfection studies showed that BMI1 inhibited cell myeloid and erythroid differentiation induced by 12-O-tetradecanoyl phorbol-13-acetate (TPA) and histone deacetylase inhibitor sodium butyrate respectively. BMI1 also resisted apoptosis induced by arsenic trioxide. Moreover, the transcript levels of Runx1 and Pten were down-regulated in Bmi1-transfected cells in company with histone deacetylation modification. By using chromatin immunoprecipitation (ChIP) collaborated with secondary generation sequencing and verified by ChIP-PCR, we found that BMI1 directly bound to the promoter region of Zmym3, which encodes a component of histone deacetylase-containing complexes. In addition, as one of the downstream target genes of this complex, c-fos was activated with increasing histone acetylation when ZMYM3 was suppressed in the Bmi1-transfected cells. These results suggested that BMI1 may reprogramme the histone acetylation profile in multiple genes through either indirect or direct binding effects which probably contributes to the malignant progression of myeloid progenitor cells.

Myelodysplastic syndrome (MDS)-associated cytogenetic abnormalities in pediatric chronic myelogenous leukemia

Chronic myelogenous leukemia (CML) is very rare in the pediatric population. We report the case of a 2-year-old female with CML and concurrent myelodysplastic syndrome (MDS) associated cytogenetic abnormalities. The co-existence of t(9;22) and chromosomal deletions that are associated with MDS poses a unique diagnostic challenge. Given the reported association of t(9;22) and genomic instability, we hypothesize that the chromosomal deletions represent clonal evolution of the CML.

Targeting developmental pathways in children with cancer: what price success?

Much of current cancer research is aimed at exploiting cancers' molecular addictions through targeted therapeutics, with notable successes documented in clinical trials. By their nature, these agents have different side-effect profiles than conventional chemotherapy drugs. Although few targeted agents have attained regulatory approval for use in children, paediatric oncologists are gaining experience with these drugs, which can have unique short-term and long-term effects in developing children that are unrecognised in adults. This Review summarises the rationale for targeted therapy, challenges in paediatric drug development, unique side-effect profiles of targeted agents, limited data from children treated with targeted agents, and implications of current knowledge and gaps therein. The demonstrated and potential effects of targeted therapies on normal tissue development and function are discussed. Future clinical trial design should include carefully considered assessment of the developmental effects of targeted therapy, and informed supportive-care recommendations.

The long-term clinical implications of clonal chromosomal abnormalities in newly diagnosed chronic phase chronic myeloid leukemia patients treated with imatinib mesylate

The aim of this study was to evaluate the long-term clinical significance of an additional chromosomal abnormality (ACA), variant Philadelphia chromosome (vPh) at diagnosis, and newly developed other chromosomal abnormalities (OCA) in patients with chronic myeloid leukemia (CML) on imatinib (IM) therapy. Sequential cytogenetic data from 281 consecutive new chronic phase CML patients were analyzed. With a median follow-up of 78.6 months, the 22 patients with vPh (P = 0.034) or ACA (P = 0.034) at diagnosis had more events of IM failure than did the patients with a standard Ph. The 5-year overall survival (OS), event-free survival (EFS), and failure-free survival (FFS) rates for patients with vPh at diagnosis were 77.8%, 75.0%, and 53.3%, respectively; for patients with ACA at diagnosis, 100%, 66.3%, and 52.1%, respectively; and for patients with a standard Ph, 96.0%, 91.3%, and 83.7%, respectively. During IM therapy, eight patients developed an OCA, which had no impact on outcomes as a time-dependent covariate in our Cox proportional hazards regression models. This study showed that vPh was associated with poor OS and FFS and that ACA had adverse effects on EFS and FFS. In addition, no OCA, except monosomy 7, had any prognostic impact, suggesting that the development of OCA may not require a change in treatment strategy.

Clonal cytogenetic abnormalities after tyrosine kinase inhibitor therapy in Ph+ ALL resolution after decitabine therapy

Mixed chimerism and presence of minimal residual disease after stem cell transplantation (SCT) usually predict leukemia recurrence. In Philadelphia chromosome positive (Ph+) leukemia tyrosine kinase inhibitors can restore remission. These agents can induce clonal cytogenetic abnormalities in the Philadelphia negative cell population (CCA/Ph-), which may rarely progress to acute myeloid leukemia. A child with Ph+ acute lymphoblastic leukemia showed mixed donor chimerism and persistent bcr-abl transcripts after a matched sibling SCT. There was no response to tyrosine kinase inhibitor (TKI) therapy, but she has remained hematologically normal for more than 5 years. CCA/Ph- was detected but resolved with hypomethylating therapy.

Telomere loss in Philadelphia-negative hematopoiesis after successful treatment of chronic myeloid leukemia: evidence for premature aging of the myeloid compartment

Telomere shortening, a well-known marker of aging and cellular stress, occurs under several conditions in the hematopoietic compartment, including aplastic anemia and following iatrogenic noxae. We decided to verify whether pathological telomere erosion also arises in restored Philadelphia-negative (Ph-negative) hematopoiesis following successful treatment of chronic myeloid leukemia (CML). Eighty-one CML patients in complete cytogenetic remission were compared to 76 age-matched healthy subjects. Myeloid cells of CML patients had shorter telomeres than controls (6521 bp vs 7233 bp, p<0.001). This difference was specific for the myeloid compartment, since it was not observed in lymphoid cells (6774 bp vs 6909 bp, p=0.620). Acquired Ph-negative cytogenetic abnormalities (p=0.010), lack of complete molecular remission (p=0.016) and age (p=0.013) were independent predictors of telomere shortening. Telomere dynamics were assessed over a median follow-up period of 22 months. We documented accelerated non-physiological ongoing telomere shortening in 17/59 CML patients (28%). Patients experiencing grade 2-4 hematological toxicity, during CML remission possessed significantly shorter telomeres compared to those lacking toxicity (p=0.005 for any toxicity, p=0.007 for anemia). CML patients suffer from significant and often ongoing telomere stress resulting in premature and selective aging of the myeloid compartment which might have long-term consequences on function and integrity of Ph-negative hematopoiesis.

How I treat newly diagnosed chronic phase CML

The progress made in the understanding of chronic myeloid leukemia (CML) since the recognition of a common chromosomal abnormality to the introduction of ever more effective tyrosine kinase inhibitors is unprecedented in cancer. The expected survival for patients diagnosed with CML today, if properly managed, is probably similar to that of the general population. When managing patients with CML the goal is to achieve the best long-term outcome and we should base the treatment decisions on the data available. The results from cytogenetic and molecular analyses have to be interpreted judiciously and all available treatment options integrated into the treatment plan properly. The availability of several treatment options in CML is an asset, but the temptation of rapid succession of treatment changes because of perceived suboptimal response or for adverse events that could be managed needs to be avoided. Any decision to change therapy needs to weigh the expected long-term outcome with the current option versus the true expectations with any new option, particularly as it relates to irreversible outcomes, such as transformation to blast phase and death. In this manuscript, we discuss the treatment approach that has helped us manage successfully a large CML population.