Monitoring of JAK2V617F allele burden in patients with essential thrombocythemia

Background/Aim This study retrospectively examined the clinical implications of monitoring JAK2V617F, with a particular focus on disease transformation, in a Korean population of patients with essential thrombocythemia (ET). Methods Medical records of patients diagnosed with ET between January 1996 and December 2021 at Chungnam National University Hospital, Daejeon, Korea, were reviewed. Both episodic changes (increase or decrease) and longitudinal patterns of change (stable, gradual increase, or gradual decrease) in JAK2V617F variant allele frequency (VAF), measured at 1-year intervals, were analyzed. Results Among the 87 patients who had JAK2V617F VAF measured at least three times, 23 (26.4%), 21 (24.1%), and 16 (18.4%) experienced increases of ≥ 25%, ≥ 50%, and ≥ 100%, respectively, while 27 (42.5%), 26 (29.9%), and 2 (2.3%) experienced decreases of ≥ 25%, ≥ 50%, and 100%, respectively. Patients with VAF increases had significantly poorer transformation-free survival than those without increases (15-year survival for ≥ 50% increase: 79.2% vs. 97.5%; p = 0.007). Regarding the longitudinal patterns, 62 (71.3%), 13 (14.9%), and 12 (13.8%) patients were classified as having stable, gradual increase, and gradual decrease patterns, respectively. Transformation-free survival was worse in patients with a gradual increase and better in those with a gradual decrease than in those with a stable pattern (20-year survival: 100% vs. 88.8% vs. 31.3%; p = 0.026). Conclusions An increasing JAK2V617F allele burden over time is associated with disease transformation in ET, supporting the need for the ongoing monitoring of JAK2V617F VAF in these patients.