Clonal Cytogenetic Abnormalities in Philadelphia Chromosome Negative Cells in Chronic Myeloid Leukemia Patients Treated with Imatinib

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.

Case report: Co-existing chronic myeloid leukemia and chronic myelomonocytic leukemia-A clinically important but challenging scenario

Chronic myeloid leukemia (CML) and chronic myelomonocytic leukemia (CMML) are two common myeloid neoplasms with overlapping morphologic features. We report a patient initially diagnosed with CML and treated with Tyrosine kinase inhibitor (TKI) but who then developed persistent monocytosis and worsening thrombocytopenia one year later. Repeat bone marrow biopsies only showed CML at the molecular level. However, markedly hypercellular bone marrow, megakaryocytic dysplasia, and SRSF2, TET2, and RUNX1 mutations by NextGen sequencing pointed to a diagnosis of CMML. For CML patients with persistent monocytosis and cytopenia, a mutational profile by NGS is helpful to exclude or identify the coexisting CMML.

An interesting case of chronic myeloid leukemia with twists and turns

Additional cytogenetic abnormalities (ACA) are known to crop up in Ph⁺ cells of chronic myeloid leukemia (CML) patients due to cytogenetic evolution. But the frequency of molecular evolution and ACA is much less in Ph^- cells of CML patients and is poorly understood. We report an interesting and rare case of Ph⁺ CML, who progressed to B lymphoblastic crisis, achieved remission, and later developed Ph^- acute myeloid leukemia (AML) with KMT2A gene rearrangement and no detectable BCR- ABL transcripts.

CML - Not only BCR-ABL1 matters

BCR-ABL1 is in the center of chronic myeloid leukemia (CML) pathology, diagnosis and treatment, as confirmed by the success of tyrosine kinase inhibitor (TKI) therapy. However, additional mechanisms and events, many of which function independently of BCR-ABL1, play important roles, particularly in terms of leukemic stem cell (LSC) persistence, primary and secondary resistance, and disease progression. Promising therapeutic approaches aim to disrupt pathways which mediate LSC survival during successful TKI treatment, in the hope of improving long-term treatment-free-remission and perhaps provide a functional cure for some patients. Over the years through advances in sequencing technology frequent molecular aberrations in addition to BCR-ABL1 have been identified not only in advanced disease but also in chronic phase CML, often affecting epigenetic regulators such as ASXL1, DNMT3A and TET2. Analyses of serial samples have revealed various patterns of clonal evolution with some mutations preceding the BCR-ABL1 acquisition. Such mutations can be considered to be important co-factors in the pathogenesis of CML and could potentially influence therapeutic strategies in the future.

Occurrence of chromosomal abnormalities in Philadelphia chromosome-negative metaphases in patients with chronic-phase chronic myeloid leukemia undergoing TKI treatments

Forty-three chromosomal abnormalities in Philadelphia-negative metaphases (Ph-CAs) appeared in 35 of 432 patients in chronic phase chronic myeloid leukemia (CP-CML) undergoing tyrosine kinase inhibitor (TKI) treatments. These CAs were mostly common in trisomy-8 (16 cases), trisomy-Y (five cases), and monosomy-7 (five cases). Furthermore, Ph- CAs were significantly associated with higher platelet count (494 × 10⁹/L vs. 326 × 10⁹/L, p = .006), and higher incidence of true clonal evolution in Ph-positive metaphase (22.9% vs. 9.1%, p = .017). Additionally, patients with Ph- CAs had worse rates of complete cytogenetic remission (76% vs. 86%, p = .0091), major molecular remission (55% vs. 76%, p = .001), progression-free survival (47% vs. 86%, p < .001), but a similar overall survival rates compared to those in patients without Ph- CAs. In conclusion, Ph- CAs may predict worse response to TKI therapies and survival in patients with CP-CML, thus requiring close cytogenetic monitoring.

Chronic myeloid leukemia with complex karyotypes: Prognosis and therapeutic approaches

OBJECTIVE AND BACKGROUND

Chronic myeloid leukemia (CML) is a neoplastic disease whose genetic and cytogenetic changes play important roles in prognosis and treatment strategies. Philadelphia (Ph) translocation t(9;22)(q34;q11) is a diagnostic and prognostic biomarker in CML.

METHODS

Pubmed and Google Scholar databases were searched for English language articles from 1975 to 2017 containing the terms CML; Additional chromosomal abnormalities; Philadelphia translocation; Prognosis; and Treatment.

DISCUSSION

Approximately 10-12% of CML patients exhibit additional chromosomal aberrations (ACAs) in chronic phase and blast crisis. ACAs emergence may cause different features in CML patients according to Ph pattern. For instance, deletion of chromosome 9 derivation is associated to patient's bad survival, whereas monosomy 7 develops myeloid dysplastic syndrome (MDS) or acute myeloid leukemia (AML) in CML patients with Ph-negative pattern. And ACAs in Ph-positive CML is considered as a failure in the management of CML with imatinib.

CONCLUSION

CML classification using different features such as Ph and ACAs can play a decisive role in the evaluation of treatment responses in patients, for example, CML patients with Ph negative and monosomy 7 develop MDS or CML patient -Y and extra copy of Ph have a good response to tyrosine kinase inhibitors, therefore, classifications according to Ph and ACAs play an important role in choosing better treatment protocols and therapeutic strategies. Karyotype analysis in CML patients with complex karyotype shows unrandom pattern so ACAs can be great clue in medical guidelines.

Incidence and outcome of second malignancies in patients with chronic myeloid leukemia during treatment with tyrosine kinase inhibitors

We performed a retrospective study to evaluate the incidence of second malignancies (SMs) in chronic myeloid leukemia (CML) patients treated with tyrosine kinase inhibitors (TKIs). We analyzed data from 339 patients with CML who were extracted from the CML Cooperative Study Group database. The standardized incidence ratio (SIR) was calculated to assess the risk of SMs using data from the Cancer Registries in Japan. The median follow-up was 65 months. SMs developed in 14 patients (4.1%, 10 men, 4 women) after the start of TKIs. The median age was 69 years at the time of the CML diagnosis and 72.5 years at the time of the SM diagnosis. Ten patients were treated with imatinib, three with dasatinib, and one with nilotinib as the initial treatment. The SIR for all malignancies was 1.05 (95% CI 0.50-1.93) for men and 1.08 (95% CI 0.29-2.76) for women. The difference in the overall survival (OS) of patients with or without SMs was not statistically significant (5-year OS: 82.5% vs. 92.9%; p = 0.343). A subgroup analysis of 166 patients treated with second-generation TKIs (92 dasatinib, 74 nilotinib) showed that the SIRs for all malignancies were 1.33 (95% CI 0.36-3.41) for men and 0 for women. In conclusion, the incidence of SMs in CML patients during TKI treatment was the same as that in the general Japanese population. There was no evidence of an increase in the incidence of SMs during second-generation TKI treatment. Furthermore, the occurrence of SMs during TKI treatment did not affect the survival or mortality in our cohort.

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.

Increased prevalence of prior malignancies and autoimmune diseases in patients diagnosed with chronic myeloid leukemia

We recently reported an increased incidence of second malignancies in chronic myeloid leukemia (CML) patients treated with tyrosine kinase inhibitors (TKI). To elucidate whether this increase may be linked, not to TKI but rather to a hereditary or acquired susceptibility to develop cancer, we estimated the prevalence of malignancies, autoimmune disease (AD) and chronic inflammatory disease (CID) in CML patients prior to their CML diagnosis. Nationwide population-based registers were used to identify patients diagnosed with CML in Sweden 2002-2012 and to estimate the prevalence of other malignancies, AD and CID prior to their CML diagnosis. For each patient with CML, five matched controls were selected from the general population. Conditional logistic regression was used to calculate odds ratios (OR). Nine hundred and eighty-four CML patients were assessed, representing more than 45 000 person-years of follow-up. Compared with matched controls, the prevalence of prior malignancies and AD was elevated in CML patients: OR 1.47 (95% confidence interval (CI) 1.20-1.82) and 1.55 (95% CI 1.21-1.98), respectively. No associations were detected between CML and previous CID. An increased prevalence of other malignancies and AD prior to the diagnosis of CML suggest that a hereditary or acquired predisposition to cancer and/or autoimmunity is involved in the pathogenesis of CML.

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.

Transient presence of clonal chromosomal aberrations in Ph-negative cells in patients with chronic myeloid leukemia remaining in deep molecular response on tyrosine kinase inhibitor treatment

Advancements in treatment of chronic myeloid leukemia (CML) turned this formerly fatal neoplasm into a manageable chronic condition. Therapy with tyrosine kinase inhibitors (TKIs) often leads to significant reduction of disease burden, known as the deep molecular response (DMR). Herein, we decided to analyze the cohort of CML patients treated in our center with TKIs, who obtain and retain DMR for a period longer than 24 months. The aim of the study was to evaluate the frequency of clonal cytogenetic aberrations in Philadelphia-negative (Ph-) cells in patients with DMR during TKI treatment. The analyzed data was obtained during routine molecular and cytogenetic treatment monitoring, using G-banded trypsin and Giemsa stain (GTG) karyotyping and reverse transcription quantitative PCR. We noticed that approximately 50% of patients (28 of 55) in DMR had, at some follow-up point, transient changes in the karyotype of their Ph- bone marrow cells. In 9.1% of cases (5 of 55), the presence of the same aberrations was observed at different time points. The most frequently appearing aberrations were monosomies of chromosomes 19, 20, 21, and Y. Statistical analysis suggests that the occurrence of such abnormalities in CML patients correlates with the TKI treatment time.

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.

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.

Management of imatinib-resistant patients with chronic myeloid leukemia

Since its approval in 2001 for frontline management of chronic myelogenous leukemia (CML), imatinib has proven to be very effective in achieving high remission rates and improving prognosis. However, up to 33% of patients will not achieve optimal response. This has led researchers to develop new second- and third-generation tyrosine kinase inhibitors. In this article, we review the mechanisms of resistance, recommendations for monitoring, assessment of milestones, and management options for patients with CML who are resistant to imatinib therapy. We further explain the potential pitfalls that can lead to unnecessary discontinuation, the prognosis of patients whose condition fails to respond to treatment, and the upcoming therapies.

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.

Karyotypic findings in chronic myeloid leukemia cases undergoing treatment

BACKGROUND:

Chronic myeloid leukemia (CML) is a clonal myeloproliferative expansion of primitive hematopoietic progenitor cells.

MATERIALS AND METHODS:

In the present study, CML samples were collected from various hospitals in Amritsar, Jalandhar and Ludhiana.

RESULTS:

Chromosomal alterations seen in peripheral blood lymphocytes of these treated and untreated cases of CML were satellite associations, double minutes, random loss, gain of C group chromosomes and presence of marker chromosome. No aberrations were observed in control samples. Karyotypic abnormalities have also been noted in the Ph-negative cells of some patients in disease remission.

CONCLUSION:

This is a novel phenomenon whose prognostic implications require thorough and systematic evaluation.

Chronic myeloid leukemia: cytogenetic methods and applications for diagnosis and treatment

Chronic myeloid leukemia (CML) is a clonal myeloproliferative disease caused by recombination between the BCR gene on chromosome 22 and the ABL1 gene on chromosome 9. This rearrangement generates the BCR-ABL1 fusion gene that characterizes leukemic cells in all CML cases. In about 90% of cases, the BCR-ABL1 rearrangement is manifest cytogenetically by the Philadelphia (Ph) chromosome, a derivative of the reciprocal translocation t(9;22)(q34;q11.2). For the remaining cases, recombination may be more complex, involving BCR, ABL1, and genomic sites on one or more other chromosomal regions, or it may occur cryptically within an apparently normal karyotype. Detection of the Ph and associated t(9;22) translocation is a recognized clinical hallmark for CML diagnosis. The disease has a natural multistep pathogenesis, and during chronic phase CML, the t(9;22) or complex variant is usually the sole abnormality. In 60-80% of cases, additional cytogenetic changes appear and often forecast progression to an accelerated disease phase or a terminal blast crisis. Because new frontline therapies such as imatinib specifically target the abnormal protein product of the BCR-ABL1 fusion gene to eliminate BCR-ABL1 positive cells, there is a new reliance on the cytogenetic evaluation of bone marrow cells at diagnosis, then at regular posttreatment intervals. Combined with other parameters, presence or absence of Ph-positive cells in the bone marrow is a powerful early indicator for clinical risk stratification. Cytogenetic changes detected at any stage during treatment, including in the BCR-ABL1-negative cells, may also provide useful prognostic information. Laboratory methods detailed here extend from initial collection of peripheral blood or bone marrow samples through cell culture with or without synchronization, metaphase or interphase harvest, hypotonic treatment and fixation, slide preparation for G-banding or fluorescent in situ hybridization (FISH), and final interpretation.

Molecular measurement of BCR-ABL transcript variations in chronic myeloid leukemia patients in cytogenetic remission

Background

The monitoring of BCR-ABL transcript levels by real-time quantitative polymerase chain reaction (RT-qPCR) has become important to assess minimal residual disease (MRD) and standard of care in the treatment of chronic myeloid leukemia (CML). In this study, we performed a prospective, sequential analysis using RT-qPCR monitoring of BCR-ABL gene rearrangements in blood samples from 91 CML patients in chronic phase (CP) who achieved complete cytogenetic remission (CCyR) and major molecular remission (MMR) throughout imatinib treatment.

Methods

The absolute level of BCR-ABL transcript from peripheral blood was serially measured every 4 to 12 weeks by RT-qPCR. Only level variations > 0.5%, according to the international scale, was considered positive. Sequential cytogenetic analysis was also performed in bone marrow samples from all patients using standard protocols.

Results

Based on sequential analysis of BCR-ABL transcripts, the 91 patients were divided into three categories: (A) 57 (62.6%) had no variation on sequential analysis; (B) 30 (32.9%) had a single positive variation result obtained in a single sample; and (C) 4 (4.39%) had variations of BCR-ABL transcripts in at least two consecutive samples. Of the 34 patients who had elevated levels of transcripts (group B and C), 19 (55.8%) had a < 1% of BCR-ABL/BCR ratio, 13 (38.2%) patients had a 1% to 10% increase and 2 patients had a >10% increase of RT-qPCR. The last two patients had lost a CCyR, and none of them showed mutations in the ABL gene. Transient cytogenetic alterations in Ph-negative cells were observed in five (5.5%) patients, and none of whom lost CCyR.

Conclusions

Despite an increase levels of BCR-ABL/BCR ratio variations by RT-qPCR, the majority of CML patients with MMR remained in CCyR. Thus, such single variations should neither be considered predictive of subsequent failure and nor an indication for altering imatinib dose or switching to second generation therapy. Changing of imatinib on the basis of BCR-ABL/BCR% sustained increase and mutational studies is a prudent approach for preserving other therapeutic options in imatinib-resistant patients.

Optimizing combination therapies with existing and future CML drugs

Small-molecule inhibitors imatinib, dasatinib and nilotinib have been developed to treat Chromic Myeloid Leukemia (CML). The existence of a triple-cross-resistant mutation, T315I, has been a challenging problem, which can be overcome by finding new inhibitors. Many new compounds active against T315I mutants are now at different stages of development. In this paper we develop an algorithm which can weigh different combination treatment protocols according to their cross-resistance properties, and find the protocols with the highest probability of treatment success. This algorithm also takes into account drug toxicity by minimizing the number of drugs used, and their concentration. Although our methodology is based on a stochastic model of CML microevolution, the algorithm itself does not require measurements of any parameters (such as mutation rates, or division/death rates of cells), and can be used by medical professionals without a mathematical background. For illustration, we apply this algorithm to the mutation data obtained in [1], [2].

Update on practical aspects of the treatment of chronic myeloid leukemia with imatinib mesylate

Imatinib (imatinib mesylate, Gleevec(R) [formerly known as STI571], Novartis Pharmaceuticals, Basel, Switzerland) is a protein tyrosine kinase inhibitor that is approved by the US Food and Drug Administration for patients with all phases of chronic myeloid leukemia (CML). Imatinib is remarkably effective as treatment for CML in the chronic phase (at a dosage of 400 mg/d) and the accelerated phase (at 600 mg/d). At this time, it remains to be seen whether the chronic phase of CML can be extended sufficiently in some patients so that they are functionally "cured," and also whether the increased rate of major molecular response induced by doses of imatinib higher than 400 mg/d will further improve overall survival of patients with CML in the chronic phase. The value of molecular monitoring of response in patients with CML in the chronic phase is examined. Although imatinib 800 mg/d can induce dramatic responses in patients with myeloid blast crisis, lymphoid blast crisis, and Philadelphia chromosome-positive acute lymphoblastic leukemia (Ph+ ALL), the responses are usually incomplete and of short duration. We discuss the role of imatinib in relation to allogeneic stem cell transplantation (particularly in younger patients), recognizing that the data upon which any decisions can be made are relatively immature. Finally, recent data on new tyrosine kinase inhibitors capable of overcoming primary or acquired resistance to imatinib are reviewed.

Clonal hematopoiesis in Philadelphia chromosome-negative bone marrow cells of chronic myeloid leukemia patients receiving dasatinib

A clonal cytogenetic abnormality was observed in Philadelphia chromosome-negative bone marrow cells of 6/27 chronic myeloid leukemia patients (+8 in 4, -7 in 1, and 20q- in 1) with dasatinib-induced remissions. The X-linked human androgen receptor gene assay demonstrated clonality in one additional patient. Single nucleotide polymorphism array analysis revealed somatic uniparental disomy involving chromosome 17(p12-pter) in another patient. The TP53 gene had a 5' splice site deletion of exon 6 that caused alternative splicing, frame shifting and introduction of a premature stop codon. After three years, no patient developed myelodysplastic syndrome or acute myeloid leukemia.

Long-term persistence of nonpathogenic clonal chromosome abnormalities in donor hematopoietic cells after allogeneic stem cell transplantation

We describe the cases of two unrelated patients who exhibited multiple chromosomal abnormalities in donor cells after allogeneic peripheral blood stem cell transplantation (PBSCT). The patients were diagnosed with chronic myeloid leukemia and chronic lymphocytic leukemia, respectively, and both underwent nonmyeloablative conditioning with cyclophosphamide and fludarabine followed by PBSCT from their HLA-matched opposite-sex siblings. Post-transplant bone marrow cytogenetics showed full engraftment, and the early post-transplant studies demonstrated only normal donor metaphases. Subsequent studies of both patients, however, revealed a population of metaphase cells with abnormal, but apparently balanced, donor karyotypes. Chromosome studies performed on peripheral blood cells collected from both donors after transplantation were normal. Both patients remained in clinical remission during follow-up of approximately 8 years in one case, and 6 years in the other case, despite the persistence of the abnormal clones. Chromosomal abnormalities in residual recipient cells after bone marrow or PBSCT are not unusual. In contrast, only rare reports of chromosome abnormalities in donor cells exist, all of which have been associated with post-bone marrow transplant myelodysplastic syndrome or acute leukemias. The present cases demonstrate the rare phenomenon of persistent clonal nonpathogenic chromosome aberrations in cells of donor origin.

Targeted treatment of chronic myeloid leukemia: role of imatinib

Chronic myeloid leukemia (CML) is a myeloproliferative disorder characterized by clonal expansion of pleuripotent hematopoetic stem cells. The incidence of CML is 1 to 2 cases per 100,000 people per year; in the Western Hemisphere, CML accounts for 15% of leukemias in adults. Discovery of the specific karyotypic abnormality of the Philadelphia (Ph) chromosome in the pathogenesis of CML has led to a better understanding of the disease and hence to an advancement of targeted therapeutics. Availability of imatinib as an accepted targeted therapy in newly diagnosed patients has changed the treatment paradigm in CML. The majority of CML patients in chronic phase achieve excellent and durable responses with standard-dose imatinib. Mechanisms of primary and secondary resistance to imatinib in CML have been extensively studied and newer tyrosine kinase inhibitors are now being evaluated for clinical use. It is important that at any time the CML treatment and response remain optimal and thus patients on imatinib require continuous monitoring for early detection of resistance. This review will discuss the treatment and guidelines for monitoring CML patients in the imatinib era.

Emerging stem cell concepts for imatinib-resistant chronic myeloid leukaemia: implications for the biology, management, and therapy of the disease

Chronic myeloid leukaemia (CML) is a myeloid neoplasm defined by the BCR/ABL oncoprotein that is considered essential for leukaemogenesis and accumulation of neoplastic cells. The BCR/ABL kinase inhibitor imatinib is an effective agent in most patients and can now be regarded as front-line therapy. Hence, intrinsic and acquired resistance to imatinib has been described and is an emerging challenge in clinical practice. While CML stem cells display primary resistance, stem cell subclones may, in addition, acquire imatinib-resistant mutants of BCR/ABL. Other factors that are considered to contribute to stem cell resistance include the genetic background, clonal evolution, additional biological features of subclones, gene amplifications, silencing of tumour suppressor genes and specific pharmacological aspects. In this article, mechanisms of resistance of CML (stem) cells against imatinib and other BCR/ABL inhibitors are discussed, together with strategies to overcome and/or to prevent resistance with available drugs or novel anti-leukaemic approaches.

Clinical and prognostic significance of histamine monitoring in patients with CML during treatment with imatinib (STI571)

BACKGROUND

Although imatinib is highly effective in chronic myeloid leukemia (CML), drug-resistance may occur. Therefore, monitoring of minimal residual disease (MRD) during treatment with imatinib is important. However, most MRD-parameters are expensive and require special technology. We determined the value of histamine as MRD-marker in CML.

PATIENTS AND METHODS

Histamine levels were measured serially in whole blood samples before and during imatinib therapy in 80 CML patients by radioimmunoassay.

RESULTS

Histamine levels were highly upregulated in CML at diagnosis compared to healthy controls, and correlated with the presence of basophils. During treatment with imatinib, histamine levels decreased and returned to normal levels in those achieving a complete cytogenetic response (CCR). Loss of CCR during therapy was invariably accompanied by an increase in histamine. Moreover, a histamine level of >100 ng/ml three or six months after start of imatinib was associated with a significantly reduced probability of survival (p<0.05). Whereas basophils were found to correlate well with histamine during imatinib, no correlations were found between histamine and Ph+ metaphases or histamine and BCR/ABL.

CONCLUSION

Histamine-monitoring during treatment with imatinib is of prognostic significance.

The prognosis for patients with chronic myeloid leukemia who have clonal cytogenetic abnormalities in philadelphia chromosome-negative cells

BACKGROUND

Clonal cytogenetic abnormalities (CCA) were detected in Philadelphia chromosome (Ph)-negative cells in some patients with chronic myeloid leukemia (CML) who attained a cytogenetic response to imatinib mesylate. In some patients, CCA/Ph-negative status was associated with myelodysplasia or acute myeloid leukemia. The objective of the current study was to determine the prognostic impact of CCA/Ph-negative cells.

METHODS

The authors compared the pretherapeutic risk factors (Kruskall-Wallis test), exposure to cytotoxic drugs (chi-square test), and overall and progression-free survival (Kaplan-Meyer and logistic regression analysis, respectively) of 515 patients with mostly chronic-phase CML who were treated with imatinib mesylate after failure of interferon-alpha according to whether they attained a major cytogenetic response (MCR) (n = 324 patients), an MCR with CCA/Ph-negative status (n = 30 patients), or no MCR (n = 161 patients).

RESULTS

CCA/Ph-negative status most frequently involved chromosomes Y, 8, and 7. No significant differences in pretherapeutic risk factors were detected between patients who attained an MCR with and without CCA/Ph-negative cells, except that exposure to alkylating agents was more frequent in patients with CCA/Ph-negative cells, and overall and progression-free survival were identical. With a median follow-up of 51 months, only 2 patients developed myelodysplastic syndromes (MDS).

CONCLUSIONS

The overall prognosis for patients who had CML with CCA/Ph-negative status was good and was driven by the CML response to imatinib mesylate. Isolated CCA/Ph-negative cells in the absence of morphologic evidence of MDS do not justify a change in therapy.

Inv (11)(p15q21) in donor-derived Ph-negative cells in a patient with chronic myeloid leukemia in relapse successfully treated with imatinib mesylate post allogeneic stem cell transplantation

Imatinib mesylate (IM) is the standard first-line treatment for patients with chronic myeloid leukemia (CML). Surprisingly, 2-15% of patients achieving a complete cytogenetic response develop cytogenetic abnormalities in Philadelphia (Ph)-negative cells. Following hematopoietic stem cell transplantation (HSCT), IM induces complete molecular responses (CMR) in approximately 70% patients with relapsed CML, and no IM-related cytogenetic abnormalities in Ph-negative donor-derived cells have been described after HSCT. We report a 56-year-old female who presented with a relapse from CML in September 2002. She had received a matched related HSCT for CML in chronic phase. Donor lymphocyte infusion was given 3 years post-HSCT for a relapse. Sustained CMR was achieved within 3 months of initiation of IM. In October 2005, routine evaluation demonstrated continuous CMR, full male donor engraftment and an inv (11) on donor cells. Evaluation of the donor demonstrated no dysplasia or cytogenetic abnormalities. This observation reinforces the possibility that IM therapy may be casually linked to the phenomenon of secondary cytogenetic changes in diploid cells.

Chromosomal abnormalities in Philadelphia chromosome negative metaphases appearing during imatinib mesylate therapy in patients with newly diagnosed chronic myeloid leukemia in chronic phase

The development of chromosomal abnormalities (CAs) in the Philadelphia chromosome (Ph)-negative metaphases during imatinib (IM) therapy in patients with newly diagnosed chronic myecloid leukemia (CML) has been reported only anecdotally. We assessed the frequency and significance of this phenomenon among 258 patients with newly diagnosed CML in chronic phase receiving IM. After a median follow-up of 37 months, 21 (9%) patients developed 23 CAs in Ph-negative cells; excluding -Y, this incidence was 5%. Sixteen (70%) of all CAs were observed in 2 or more metaphases. The median time from start of IM to the appearance of CAs was 18 months. The most common CAs were -Y and + 8 in 9 and 3 patients, respectively. CAs were less frequent in young patients (P = .02) and those treated with high-dose IM (P = .03). In all but 3 patients, CAs were transient and disappeared after a median of 5 months. One patient developed acute myeloid leukemia (associated with - 7). At last follow-up, 3 patients died from transplantation-related complications, myocardial infarction, and progressive disease and 2 lost cytogenetic response. CAs occur in Ph-negative cells in a small percentage of patients with newly diagnosed CML treated with IM. In rare instances, these could reflect the emergence of a new malignant clone.

Characterization of Ph-negative abnormal clones emerging during imatinib therapy

BACKGROUND

Imatinib is a tyrosine kinase-specific inhibitor widely used for the treatment of chronic myeloid leukemia (CML). Studies reported the occurrence of additional cytogenetic abnormalities in the Philadelphia chromosome (Ph)-negative cell population emerging after treatment-induced suppression of the Ph-positive clone. These abnormalities were described in a relatively high proportion of patients treated with imatinib compared with the anecdotal reports of similar cases in patients treated with other drugs. However, the origin of these abnormalities as well as their biological and clinical significance are unknown.

METHODS

The study involved 13 cases of patients diagnosed with CML carrying cytogenetic abnormalities in their Ph-negative cell population after imatinib treatment. The presence of the markers within the CD34+ stem cell compartment and the cell culture growth were analyzed and patients were followed over time.

RESULTS

CD34+ cells express the cytogenetic markers present in Ph- cells, suggesting a possible involvement of the stem cell population. Cultured cells showed normal growth in all but 1 patient. No growth advantage was demonstrated for the Ph-negative or the Ph-positive clone after cell culture.

CONCLUSIONS

After follow-up of up to 49 months, none of the patients had evolved to myelodysplasia or acute leukemia. Hypothesis regarding the biological and clinical significance of these abnormalities are formulated.

An inv(16) in Ph-negative cells of a chronic myelogenous leukemia patient after imatinib treatment

Secondary chromosomal changes are known to develop in Philadelphia chromosome-negative (Ph-) cells of chronic myelogenous leukemia (CML) patients after treatment with imatinib mesylate, an ABL kinase inhibitor. We report here a novel case of a pericentric inversion of chromosome 16 as the sole cytogenetic abnormality in Ph- cells after treatment of Ph+ CML with imatinib.