Risk stratification for survival and leukemic transformation in essential thrombocythemia: a single institutional study of 605 patients

Unlike the case with thrombosis, prognostic models for survival and leukemic transformation ( LT) in essential thrombocythemia ( ET) are not available. Among 605 patients with ET seen at our institution and followed for a median of 84 months, 155 died and LT was documented in 20 patients (3.3%). In a multivariable analysis, hemoglobin level below normal ( females < 120 g/l; males < 135 g/l) was identified as an independent risk factor for both inferior survival and LT. Additional risk factors for survival included age >= 60 years, leukocyte count >= 15 x 10(9)/l, smoking, diabetes mellitus and thrombosis. For LT, platelet count >= 1000 x 10(9)/l but not cytoreductive therapy was flagged as an additional independent risk factor. In fact, four of the 20 patients (20%) with LT were untreated previously. We used the above information to construct prognostic models that effectively discriminated among low-, intermediate- and high-risk groups with respective median survivals of 278, 200 and 111 months (P < 0.0001), and LT rates of 0.4, 4.8 and 6.5% (P = 0.0009) respectively. Presence of JAK2V617F did not impact either survival or LT and mutational frequency was similar among the different risk groups.