Treatment of essential thrombocythemia in Europe: a prospective long-term observational study of 3649 high-risk patients in the Evaluation of Anagrelide Efficacy and Long-term Safety study

Abstract

Evaluation of Anagrelide (Xagrid^®) Efficacy and Long-term Safety, a phase IV, prospective, non-interventional study performed in 13 European countries enrolled high-risk essential thrombocythemia patients treated with cytoreductive therapy. The primary objectives were safety and pregnancy outcomes. Of 3721 registered patients, 3649 received cytoreductive therapy. At registration, 3611 were receiving: anagrelide (Xagrid^®) (n=804), other cytoreductive therapy (n=2666), or anagrelide + other cytoreductive therapy (n=141). The median age was 56 vs. 70 years for anagrelide vs. other cytoreductive therapy. Event rates (patients with events/100 patient-years) were 1.62 vs. 2.06 for total thrombosis and 0.15 vs. 0.53 for venous thrombosis. Anagrelide was more commonly associated with hemorrhage (0.89 vs. 0.43), especially with anti-aggregatory therapy (1.35 vs. 0.33) and myelofibrosis (1.04 vs. 0.30). Other cytoreductive therapies were more associated with acute leukemia (0.28 vs. 0.07) and other malignancies (1.29 vs. 0.44). Post hoc multivariate analyses identified increased risk for thrombosis with prior thrombohemorrhagic events, age ≥65, cardiovascular risk factors, or hypertension. Risk factors for transformation were prior thrombohemorrhagic events, age ≥65, time since diagnosis, and platelet count increase. Safety analysis reflected published data, and no new safety concerns for anagrelide were found. Live births occurred in 41/54 pregnancies (76%). clinicaltrials.gov Identifier: 00567502.

Trial registration: ClinicalTrials.gov NCT00567502.

Figure 1.

Treatment at registration vs. age. Patients in various age groups were treated at registration with anagrelide, hydroxycarbamide, interferon, combination therapy or other monotherapy. *Includes busulfan, interferon, pipobroman, P32, thromboreductin (anagrelide).

Figure 2.

Median blood cell counts over time by first-treatment analysis population. An ad hoc analysis was performed to exclude extreme laboratory data attributed to data entry errors based on the following thresholds: platelet counts of <10×10⁹/L or >10,000×10⁹/L, white blood cell counts of <0.5×10⁹/L or >150×10⁹/L, hemoglobin of <5 g/dL or >22 g/dL, and hematocrit at <10% or >70%. Removal of outliers resulted in similar median results. ANA: anagrelide.