Association between JAK2V617F variable allele frequency and risk of thrombotic events in patients with myeloproliferative neoplasms.

BACKGROUND: Myeloproliferative neoplasms (MPNs) are a group of chronic disorders of the bone marrow characterised by the overproduction of clonal myeloid stem cells. The most common driver mutation found in MPNs is a point mutation on exon 14 of the JAK2 gene, JAK2V617F. Various studies have suggested that measuring the variable allele frequency (VAF) of JAK2V617F may provide useful insight regarding diagnosis, treatment, risks and outcomes in MPN patients. In particular, JAK2V617F has been associated with increased risk of thrombotic events, a leading cause of mortality in MPNs. AIMS: The aim of this study was to determine if JAK2V617F VAF was associated with clinical outcomes in patients with MPN. METHODS: JAK2V617F VAF was determined by quantitative PCR (qPCR) in a cohort of 159 newly diagnosed MPN patients, and the association of JAK2V617F VAF and risk of thrombosis was examined in this cohort. RESULTS: We observed a significantly higher JAK2V617F VAF in PV and PMF versus ET. A significant association was observed between JAK2V617F VAF and risk of thrombotic events. When patients were stratified by thrombotic events prior to and post diagnosis, an association with JAK2V617F VAF was only observed with post diagnosis thrombotic events. Of note, these associations were not observed when looking at each MPN subtype in isolation. CONCLUSIONS: We have shown that a higher JAK2V617F VAF is associated with thrombotic events post MPN diagnosis. JAK2V617F VAF may therefore provide a valuable prognostic indicator for risk of thrombosis in MPNs.

Mutational profiling in suspected triple-negative essential thrombocythaemia using targeted next-generation sequencing in a real-world cohort.

Essential thrombocythaemia (ET) is driven by somatic mutations involving the JAK2, CALR and MPL genes. Approximately 10% of patients lack driver mutations and are referred as 'triple-negative' ET (TN-ET). The diagnosis of TN-ET, however, relies on bone marrow examination that is not always performed in routine practice, and thus in the real-world setting, there are a group of cases with suspected TN-myeloproliferativeneoplasm.In this real-world cohort, patients with suspected TN-ET were initially rescreened for JAK2, CALR and MPL and then targeted next-generation sequencing (NGS) was applied.The 35 patients with suspected TN-ET had a median age at diagnosis of 43 years (range 16-79) and a follow-up of 10 years (range 2-28). The median platelet count was 758×109/L (range 479-2903). Thrombosis prior to and following diagnosis was noted in 20% and 17% of patients. Six patients were JAK2V617F and two patients were CALR positive on repeat screening. NGS results showed that 24 of 27 patients harboured no mutations. Four mutations were noted in three patients.There was no evidence of clonality for the majority of patients with suspected TN-ET with targeted NGS analysis. Detection of driver mutations in those who were previously screened suggests that regular rescreening is required. This study also questions the diagnosis of TN-ET without the existence of a clonal marker.

Response to Imatinib therapy is inferior for e13a2 BCR-ABL1 transcript type in comparison to e14a2 transcript type in chronic myeloid leukaemia.

BACKGROUND: The BCR-ABL1 fusion gene underlying the pathogenesis of CML can arise from a variety of breakpoints. The e13a2 and e14a2 transcripts formed by breakpoints occurring around exon 13 and exon 14 of the BCR gene respectively are the most common. METHODS: We undertook a retrospective audit using local laboratory database and electronic patient care records of 69 CML patients with an e13a2 or e14a2 transcript type identified in our regional population. RESULTS: The e13a2 group was on average significantly younger (45.0 years v 54.5 years), had a higher average white cell count (189.8 × 109/l v 92.40 × 109/l) and lower platelet count (308 × 109/l v 644 × 109/l) in comparison to the e14a2 group suggesting that these are distinct biological entities. Over an average follow-up of 33.8 months and 27.2 months for the e13a2 and e14a2 groups we observed an inferior molecular response to imatinib in the e13a2 group. A significantly lower number of patients in the e13a2 arm met European Leukemia Net criteria for optimal response at 12 months therapy (17.64% v 50.0%) and were slower to obtain deep molecular responses MR4 or MR4.5. CONCLUSION: Patients with an e13a2 transcript demonstrate an inferior molecular response to imatinib in our regional population.