Emergence of chronic myelogenous leukemia in a patient with primary thrombocythemia and absence of BCR/ABL rearrangement

A Case of Chronic Myelogenous Leukemia Occurring in a Patient Treated for Essential Thrombocythemia

Patient: Female, 49

Final Diagnosis: Essential thrombocythemia with CML

Symptoms: Decreased appetite • fatigue • weight loss

Medication: —

Clinical Procedure: —

Specialty: Hematology

Coexisting driver mutations in MPN: clinical and molecular characteristics of a series of 11 patients

OBJECTIVES

CML, PV, ET and PMF are so called classical MPN with distinct clinical phenotypes. The discovery of the BCR-ABL1 translocation and mutations in driver genes JAK2, MPL and CALR has provided novel insights in their pathogenesis. While these mutations are thought to be mutually exclusive, rare cases of MPN with coexisting driver mutations have been reported. However, little is known about the clinical, biological and molecular characteristics of these patients and the interaction of the neoplastic clones.

METHODS

We retrospectively studied 11 MPN patients with coexisting driver mutations (JAK2 V617F + BCR-ABL1: n = 8; CALR type 2 + BCR-ABL1: n = 1; JAK2 V617F + MPL W515: n = 1; JAK2 V617F + CALR type 1: n = 1). To assess possible associated molecular aberrations, we analysed DNA of six patients using NGS.

RESULTS

In four CML patients, decreasing BCR-ABL1 transcript levels with increasing JAK2 V617F allele burden under TKI were observed. This strongly suggests that the coexistence of driver mutations originates from two different clones growing independently. Additional somatic mutations were detected in 5 out of 6 (83%) patients affecting 4 different genes, confirming the heterogeneity of this study cohort. Suboptimal response to TKI was observed with a higher frequency (4/8 patients) than reported in conventional series of CML and the overall tolerance of treatment with hydroxyurea and/or imatinib in our series was poor.

CONCLUSION

Given the emergence of NGS in clinical practice, more similar cases will be identified in the coming years. The optimal treatment strategy for this rare group of patients is uncertain and toxicity of combination treatment may have to be considered.

Emergence of chronic myelogenous leukemia from a background of myeloproliferative disorder: JAK2V617F as a potential risk factor for BCR-ABL translocation

We report the emergence of chronic myelogenous leukemia (CML) in a patient with JAK2V617F-positive polycythemia vera after 15 years of phlebotomy. The polycythemia vera clinical and molecular findings were suppressed at the time of CML diagnosis, only to re-emerge after the leukemia was successfully treated with imatinib. We explored the potential association between myeloproliferative disorders and CML in the context of the current literature and found a higher-than-expected coincidence based on known epidemiologic data for each specific condition. We hypothesize that myeloproliferative disorder (JAK2V617F or molecular events that cause JAK2V617F) is a risk factor for CML (BCR-ABL translocation). Because of therapeutic implications, clinicians should be aware that the conditions co-occur more frequently than once thought.

Emergence of chronic myelogenous leukemia during treatment for essential thrombocythemia

A 72-year-old male patient was initially diagnosed with essential thrombocythemia (ET), a Philadelphia chromosome-negative (Ph1(-)) chronic myeloproliferative disorder (CMPD), and was treated with hydroxyurea (HU). After 9 years of diagnosis of ET, his peripheral leukocytes gradually increased, while his platelet count showed a decrease. Bone marrow analysis disclosed Ph-positive chronic myelogenous leukemia (CML) in the chronic phase. Administration of imatinib mesylate (IM), a Bcr-Abl tyrosine kinase inhibitor (TKI), induced complete hematologic response in a month, but was discontinued after 4 months because of Grade 3 pleural effusion (PE). The treatment was switched to nilotinib which successfully induced a complete cytogenetic response (CCyR) after 5 months of TKI therapy and resolved the PE. Despite CCyR, however, ET recurred. Since then, the patient has been treated for 8 months with a combination of nilotinib and HU which has successfully controlled both CML and ET. This report includes a review of the characteristics of 15 reported cases with co-occurrence of CML and Bcr-Abl-negative CMPDs, including ours. Although rare, care needs to be taken since, despite the often similar clinical features of the two diseases, they require completely different treatments.