By Melissa Badamo – Last Updated: May 27, 2025
While cytoreductive drugs did not reduce thrombosis risk in adolescent and young adult (AYA) patients with essential thrombocythemia (ET) and polycythemia vera (PV), interferon “significantly improved” myelofibrosis-free survival (MFS) compared with other treatments, according to a study published in Leukemia.
The retrospective study explored the long-term complications and impact of cytoreductive drugs on patient outcomes, thrombotic risk, and progression to secondary myelofibrosis (sMF) in 348 patients diagnosed with ET (n=278) or PV (n=70) before the age of 25 years. The primary end points were MFS, thrombosis-free survival (TFS), and overall survival. Secondary end points included identification of risk factors associated with thrombotic events and progression to sMF.
In the ET cohort, 147 (53%) patients had JAK2 mutations, 43 (16%) had CALR mutations, 3 (1%) had MPL mutations, and 85 (30%) were triple negative (TN). All patients with PV had JAK2 mutations.
A total of 237 (68%) patients were treated with a cytoreductive drug, including 185 patients with ET (66.5%) and 52 patients with PV (74.3%). Patients received one line of therapy (n=97; 41%), two lines of therapy (n=82; 35%), or three or more lines of therapy (n=58; 24%). The most prescribed first-line treatments were hydroxycarbamide (n=126; 53%), interferon (n=55; 23%), anagrelide (n=52; 22%), and alternative drugs (n=4; 2%). The median follow-up was 8.5 years.
Thrombotic Risk
Forty-four patients presented 57 thrombotic events, with a risk of 1.9 per 100 patient-years. The 10- and 20-year probability of TFS was 86.8% and 78.8% for the entire cohort, 86.9% and 80.0% for patients with ET, and 84.4% and 76.3% for patients with PV.
In a multivariate analysis, elevated white blood cell count (>11 × 109/L; hazard ratio [HR], 2.7; P=0.012) and the absence of splenomegaly at diagnosis (HR, 5.7; P=0.026) were associated with increased risk for thrombosis.
Choice of first treatment did not correlate with differences in TFS. The 10- and 20-year TFS were 83.9% and 79.9% for interferon, 81.4% and 70.2% for hydroxycarbamide, and 91.6% and 76.3% for anagrelide (P=0.281)