PB1956 COEXISTENCE OF BCR/ABL1 AND JAK2 MUTATION IN MYELOPROLIFERATIVE NEOPLASMS

Background:Chronic Myeloid Leukemia and Myeloproliferative neoplasms were considered mutually exclusive. However some recent reports have described the co‐occurrence of BCR/ABL1 and JAK2 mutation in patients with CML phenotype. Generally, in the few reported cases, clinical and laboratory data suggest the presence of two different clones.Aims:Here we describe the clinical and molecular data of 3 patients showing the presence of BCR/ABL1 and JAK 2 mutation, with CML phenotype in 1 and myeloproliferative phenotype evolving in CML in the others.Methods:BCR/ABL1 transcript were identified and quantified by Rq‐PCR according to ELN recommendations; JAK2 mutation were evidenced by PNA clamping PCR in one patient and by ASO‐PCR in the others.Results:Patient clinical characteristics are summarized in table 1. Patient 1 showed CML phenotype with coexistence of BCR/ABL1 and JAK2 mutation at diagnosis. He started Dasatinib treatment at standard dose (100 mg/die) but after 6 months because of intolerance, he switched to Ponatinib obtaining a major molecular response. Patient 2 was diagnosed Thrombocytemia carrying V617F JAK2 mutation, after a portal vein thrombosis and started anticoagulant therapy combined to Hydroxiurea treatment. After 2 years, he switched to IFN therapy and in 2011 (after 2 more years) he showed CML feature with the appearance of BCR/ABL1 hybrid transcript. Imatinib treatment was added to Interferon and combination therapy was sustained for 7 years. Because of intolerance to IFN, in 2018 patient switched to Ruxolitinib at the dose of 30 mg BID, while also maintaining Imatinib. Patient 3 was diagnosed Thrombocytemia carrying V617F JAK2 mutation in 2009 and received IFN treatment. In 2017 he developed leukocytosis with the appearance of e1a2 BCR/ABL1 hybrid transcript. At that time, he stopped IFN therapy and started Imatinib at the standard dose of 400 mg per day with control of both diseases. Molecular monitoring showed a simultaneous decrease of both abnormalities in patient 1 who got a deep molecular response (MR 4). Patient 2 reached a deep molecular response (MR 4.5) but still needs of Ruxolitinib treatment for thrombocytemia, suggesting the presence of two different clones. Patient 3 got a deep molecular response (MR 5) and it is ongoing the evaluation of JAK2 mutation.Summary/Conclusion:Coexistence of BCR/ABL1 and JAK2 mutation is rarely reported so far but a widely use of molecular techniques could increase the number of patients with both abnormalities. At least in patient 3 of our series, clinical and molecular data suggest that both abnormalities are present in the same clone and V617F JAK2 mutation is the first occurred one. Digital PCR experiments could clarify if a single cell express both molecular abnormalities. Such cases are relevant to better understand the pathogenesis of myeloproliferative neoplasms.