First and second line imatinib treatment in chronic myelogenous leukemia patients expressing rare e1a2 or e19a2 BCR–ABL transcripts

Chronic Myelogenous Leukemia with Double Philadelphia Chromosome and Coexpression of p210 and p190 Fusion Transcripts

The Philadelphia (Ph+) chromosome, t(9;22)(q34;q11.2), originates from a chimeric gene called BCR-ABL and is present in more than 90% of CML patients. Most patients with CML express the protein p210 BCR-ABL and, with a frequency lower than 5%, express rare isoforms, the main one being p190. In the transition from the chronic phase to the blast phase (BP), additional chromosomal abnormalities, such as the presence of the double Ph+ chromosome, are revealed. Of the 1132 patients analyzed via molecular biology in this study, two patients (0.17%) showed the co-expression of the p210 and p190 isoforms for the BCR-ABL transcript, with the concomitant presence of a double Ph+ chromosome, which was observed via conventional cytogenetics and confirmed by fluorescent in situ hybridization. The BCR-ABL/ABL% p210 and p190 ratio increased in these two patients from diagnosis to progression to blast crisis. To our knowledge, this is the first report in the literature of patients who co-expressed the two main BCR-ABL transcript isoforms and concomitantly presented Ph+ chromosome duplication. The evolution from the chronic phase to BP often occurs within 5 to 7 years, and, in this study, the evolution to BP was earlier, since disease-free survival was on average 4.5 months and overall survival was on average 9.5 months. The presence of the p190 transcript and the double Ph+ chromosome in CML may be related to the vertiginous progression of the disease.

Ponatinib induces a sustained deep molecular response in a chronic myeloid leukaemia patient with an early relapse with a T315I mutation following allogeneic hematopoietic stem cell transplantation: a case report

Background

Atypical BCR-ABL1 transcripts are detected in less than 5% of patients diagnosed with chronic myeloid leukaemia (CML), of which e19a2 is the most frequently observed, with breakpoints in the micro breakpoint cluster region (μ-BCR) and coding for the p230 BCR-ABL1 protein. p230 CML is associated with various clinical presentations and courses with variable responses to first-line imatinib.

Case presentation

Here we report a case of imatinib resistance due to an E255V mutation, followed by early post-transplant relapse with a T315I mutation that achieved a persistent negative deep molecular response (MR^5.0) after treatment with single-agent ponatinib. Using CastPCR, we could trace back the presence of the T315I mutation to all the RNA samples up to the detection of T315 mutation by Sanger sequencing shortly after allogeneic hematopoietic stem cell transplantation (HSCT).

Conclusion

This case illustrates the major interest of ponatinib as a valid treatment option for e19a2 CML patients who present a T315I mutation following relapse after HSCT.

Electronic supplementary material

The online version of this article (10.1186/s12885-018-5100-4) contains supplementary material, which is available to authorized users.

Clinical Features and Treatment Outcomes of 51 Patients with Chronic Myeloid Leukemia Treated with a Tyrosine Kinase Inhibitor at a Single Institution from 2002 to 2014

Although clinical trials of first- and second-generation tyrosine kinase inhibitors (TKIs) have been shown to improve the prognosis of chronic myeloid leukemia (CML), there is still uncertainty about the clinical features, treatment outcomes, adverse effects, and other possible problems of their use in the clinical setting. We retrospectively analyzed 51 CML patients treated with TKIs at a single institution between 2002 and 2014. The patients (median age: 53.8 years) were classified as having chronic (n = 48), accelerated (n = 2), or blastic phase (n = 1) CML. Our treatments included both 1st generation TKIs (60.8%) and 2nd generation TKIs (39.2%). We found that the overall response rates of complete cytogenetic response (CCyR), major molecular response (MMR), and MR4 (molecular response 4) were 90.2%, 78.4%, and 64.7%, respectively. Second line 2nd generation TKIs had response rates equivalent to those of 1st line 1st generation TKIs. Moreover, 1st line 2nd generation TKIs tended to achieve an early response rate. Overall survival (OS) at 5 years was 93.2%. Sudden blastic crisis (BC) occurred in 2 CML patients receiving TKI with CCyR status. Hematopoietic stem cell transplantation was performed for BC (n = 1) and sudden BC (n = 2). Side effects of all grades (1-3) and grade 3 alone were 64.7% and 11.8%, respectively. Dose reduction, replacement with another TKI, or low dose TKI treatment may be useful methods to control side effects. Further reasons of TKI discontinuation were economic problems (n = 3) and pregnancy (n = 1). Consequently, our treatment strategy for CML demonstrated good response rate and OS. Currently, treatment discontinuation due to intolerance, resistance, economic problems, pregnancy, and sudden BC remains a concern in clinical practice.

Rapid Evolution to Blast Crisis Associated with a Q252H ABL1 Kinase Domain Mutation in e19a2 BCR-ABL1 Chronic Myeloid Leukaemia

A minority of chronic myeloid leukaemia (CML) patients express variant transcripts of which the e19a2 BCR-ABL1 fusion is the most common. Instances of tyrosine kinase inhibitor (TKI) resistance in e19a2 BCR-ABL1 CML patients have rarely been reported. A case of e19a2 BCR-ABL1 CML is described in whom imatinib resistance, associated with a Q252H ABL1 kinase domain mutation, became apparent soon after initiation of TKI therapy. The patient rapidly transformed to myeloid blast crisis (BC) with considerable bone marrow fibrosis and no significant molecular response to a second generation TKI. The clinical course was complicated by comorbidities with the patient rapidly succumbing to advanced disease. This scenario of Q252H-associated TKI resistance with rapid BC transformation has not been previously documented in e19a2 BCR-ABL1 CML. This case highlights the considerable challenges remaining in the management of TKI-resistant BC CML, particularly in the elderly patient.

Chronic Myeloid Leukemia with e19a2 BCR-ABL1 Transcripts and Marked Thrombocytosis: The Role of Molecular Monitoring

While most patients with chronic myeloid leukemia (CML) express either e13a2 or e14a2 BCR-ABL1 transcripts, a significant minority expresses variant transcripts, of which e19a2 is the most common. Although considered to have a relatively favourable outcome, reported responses to tyrosine kinase inhibitor (TKI) therapy are variable with molecular monitoring in CML patients with e19a2 BCR-ABL1 transcripts rarely reported. A case of e19a2 BCR-ABL1 CML with marked thrombocytosis is described in which the value of molecular monitoring is emphasised during treatment interruptions, dose reductions, and changes. This case serves to demonstrate the requirement for prospective real-time quantitative PCR (RQ-PCR) assays for patients with variant BCR-ABL1 transcript types and standardisation of such assays to enable modern patient management.

ABL1 fusion genes in hematological malignancies: a review

Chromosomal rearrangements involving the ABL1 gene, leading to a BCR-ABL1 fusion gene, have been mainly associated with chronic myeloid leukemia and B-cell acute lymphoblastic leukemia (ALL). At present, six other genes have been shown to fuse to ABL1. The kinase domain of ABL1 is retained in all chimeric proteins that are also composed of the N-terminal part of the partner protein that often includes a coiled-coil or a helix-loop-helix domain. These latter domains allow oligomerization of the protein that is required for tyrosine kinase activation, cytoskeletal localization, and neoplastic transformation. Fusion genes that have a break in intron 1 or 2 (BCR-ABL1, ETV6-ABL1, ZMIZ1-ABL1, EML1-ABL1, and NUP214-ABL1) have transforming activity, although NUP214-ABL1 requires amplification to be efficient. The NUP214-ABL1 gene is the second most prevalent fusion gene involving ABL1 in malignant hemopathies, with a frequency of 5% in T-cell ALL. Both fusion genes (SFPQ-ABL1 and RCSD1-ABL1) characterized by a break in intron 4 of ABL1 are associated with B-cell ALL, as the chimeric proteins lacked the SH2 domain of ABL1. Screening for ABL1 chimeric genes could be performed in patients with ALL, more particularly in those with T-cell ALL because ABL1 modulates T-cell development and plays a role in cytoskeletal remodeling processes in T cells.

E355G mutation appearing in a patient with e19a2 chronic myeloid leukaemia resistant to imatinib

The development of imatinib is a milestone in the treatment of chronic myeloid leukaemia (CML), and its therapeutic effect has been extensively investigated in patients with CML who carry M-bcr and m-bcr BCR-ABL fusion transcripts. However, knowledge about its therapeutic effect on patients with CML who have the rare BCR-ABL fusion transcript e19a2 (mu-bcr) remains sparse. This report describes a patient with Philadelphia-positive chronic myeloid leukaemia with e19a2 rearrangement, in whom E355G mutation had been acquired. The patient was resistant to imatinib treatment based on conventional cytogenetic and fluorescence in situ hybridisation analysis.

Chronic myeloid leukemia (CML) with P190 BCR-ABL: analysis of characteristics, outcomes, and prognostic significance

The most common BCR-ABL transcripts in chronic myeloid leukemia (CML) are e13a2(b2a2) and e14a2(b3a2). Other transcripts such as e1a2 are rare and their outcome with tyrosine kinase inhibitors (TKI) therapy is undefined. We analyzed 1292 CML patients and identified 14 with only e1a2 transcripts, 9 in chronic phase (CP), 1 in accelerated phase (AP), and 4 in blast phase (BP). Of the CP, 4 achieved complete hematologic response (CHR); 2, complete cytogenetic response (CCyR); 2, partial cytogenetic response (PCyR), and 1 did not respond to imatinib. Five patients progressed to myeloid BP (3), lymphoid BP (1), or AP (1). The AP patient received various TKIs sequentially and achieved only CHR. BP patients received hyper-CVAD (hyperfractionated cyclophosphamide, vincristine, adriamycin, dexamethasone) plus imatinib/dasatinib or idarubicin plus cytarabine (Ara-C); 2 did not respond, 1 had CCyR, and 1 short-lasting complete molecular response (CMR). Overall, cytogenetic responses lasted 3 to 18 months; only 2 achieved major molecular response (MMR) on TKI. P190(BCR-ABL) CML is rare and is associated with an inferior outcome to therapy with TKI. These patients need to be identified as high-risk patients.

Molecular response to imatinib in patient with Ph negative p190 BCR-ABL transcript positive chronic myeloid leukemia with cyclic leukocytosis

An atypical case of Philadelphia (Ph) negative, e1a2 BCR-ABL transcript positive chronic myeloid leukemia (CML) characterized with cyclic periodic leukocytosis and spontaneous remissions is reported. The patient was treated with imatinib and good hematology response with molecular remission was achieved. So far, only few Ph positive CML patients expressing p190 BCR-ABL protein and different clinical characteristics and treatment have been described in the literature. This is the first report of Philadelphia negative, p190 BCR-ABL positive CML with cyclic spontaneous oscillation of white blood cell count (WBC), and excellent response to imatinib treatment.