Prognostic value of modified criteria for hydroxyurea resistance or intolerance in patients with high-risk essential thrombocythemia

Data from a retrospective study of the development of hydroxyurea (HU) resistance/intolerance—according to the European LeukemiaNet (ELN) and the modified ELN (mELN) criteria—among patients with ET showed that HU resistance defined by the mELN criteria but not the ELN criteria was an independent prognostic factor for transformation-free survival. Using the ELN criteria, transformation to myelofibrosis and AML occurred in 2 (1.4%) patients and 1 (0.7%) patient, respectively, compared with 3 (2.1%) and 2 (1.4%) patients using the mELN criteria. Additionally, when applying the mELN criteria to patients with ET, 22 patients (15%) were deemed resistant and 8 patients (5.5%) intolerant, compared to 10 patients (6.9%) and 5 patients (3.4%), respectively, when the ELN criteria was applied.