[Retrospective analysis of the efficacy and tolerability of anagrelide in patients with essential thrombocytemia: Spanish registry of essential thrombocytemia]. / Análisis retrospectivo de la eficacia y la tolerabilidad de anagrelida en pacientes con trombocitemia esencial: registro español de trombocitemia esencial.

BACKGROUND AND OBJECTIVE: A retrospective analysis of a registration database was used to assess the efficacy and tolerability of anagrelide for treating essential thrombocythemia (ET). The study was conducted by analysing information on response to treatment, time to response and tolerability. PATIENTS AND METHOD: A total of 411 patients with ET from 54 centres in Spain were included in a retrospective chart review. Patients who had started treatment with anagrelide as a first- or second-line therapy before December 31, 2004 were included. RESULTS: Of 411 patients, anagrelide was given as a first-line therapy in 110 patients, following hydroxyurea in 280 patients, and following other drugs in 21 patients. Overall response (OR) with anagrelide was 81.2% (77,0-84,9; p=0,05). Complete response (platelets <400x10(9)/L) was observed in 53.6% (48,6-58,5; p=0,05) and partial response (<600x10(9)/L) in 27.6% (23,4-32,2; p=0,05) of patients. There was no significant correlation of previous treatment with OR rate (p=0.103) despite a higher OR for previously untreated patients (86.4%) than for previously treated patients (79.3%). The most frequent treatment-related adverse reactions were headache (13.1%), palpitations (10.2%) and tachycardia (7.5%). CONCLUSIONS: The observed response rates and tolerability profile are similar to those reported previously. Anagrelide is well tolerated and effective in reducing platelets to target levels in patients with ET.