No Differences in Outcomes Between JAK2 V617F-Positive Patients with Variant Allele Fraction < 2% Versus 2-10%: A 6-Year Province-wide Retrospective Analysis.

JAK2 V617F mutation is one of the major criteria in the diagnosis of myeloproliferative neoplasms (MPN) and its variant allele fraction (VAF) determines the disease phenotype and outcomes. This study aimed to define characteristics and outcomes of patients with JAK2 V617F VAF < 2% compared to patients with VAF 2%-10%. We included 5079 patients with JAK2 V617F tested during 2010-2015 and identified 216 patients (4.3%) with JAK2 V617F VAF < 10%. Twenty-seven patients were excluded because of missing follow-up data. A total of 189 patients were included for final analysis (89 patients with VAF < 2% and 100 patients with VAF 2%-10%). Patients with JAK2 V617F 2%-10% VAF had a significantly higher rate of splenomegaly, higher platelet counts, and more MPN diagnoses than the group with VAF < 2%. Ten patients (10.0%) with VAF 2%-10% and 24 patients (27.0%) with VAF < 2% had normal blood count and no thrombosis. There were no differences between the groups in all outcomes, including thrombotic complications (18.0% in both groups), progression to hematologic or solid cancers, and death. Patients without hematologic diagnosis had similar thrombotic incidence (16.7% in VAF < 2% vs. 20.0% in VAF 2%-10%). Patients with JAK2 V617F mutation VAF < 2% have similar survival and thrombotic incidence as patients with VAF 2%-10%. Patients with low VAF should be monitored in the same manner as patients with higher VAF with the same diagnoses to prevent morbidity and mortality. Patients without hematologic diagnosis may benefit from thrombotic risk reduction strategies such as optimization of cardiovascular risk factors.

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