Ernesto Di Francesco

Effects of anagrelide on platelet factor 4 and vascular endothelial growth factor levels in patients with essential thrombocythemia

The management of essential thrombocythemia (ET) includesalkylating agents, hydroxyurea (HU) and interferon-a (IFN-a)alone or in combination with anti-aggregants (Spivak et al,2003). It has been demonstrated that ET patients receivingcytoreduction and anti-aggregants show increased plateletfactor 4 (PF4) levels despite clinical remission (Bellucci et al,1993). Anagrelide is a platelet-lowering drug that inhibitsplatelet aggregation (Spivak et al, 2003). Therefore, we eval-uated the platelet count and PF4 levels in ET patients treatedeither with HU, IFN-a or anagrelide in combination with anti-aggregants. Activated platelets release vascular endothelialgrowth factor (VEGF), which is increased in ET (Mesa et al,2000). Thus, we also determined the corrected platelet VEGFlevel (VEGF

Effect of Anagrelide on Platelet Coagulant Function in Patients with Essential Thrombocythemia

Group and the WHO [7] . The mean duration of disease was 6 years (range 2–18). Seventeen patients received HU (8 men, 9 women; mean age 68 years), and 19 patients were on ANA (12 men, 7 women; mean age 61 years). Their main characteristics are listed in table 1 . The average dose of HU was 0.5 g/day (range 0.25–1.00). ANA was initially administered at a dose of 0.5 mg/day. Subsequently, the dose was increased by 0.5 mg/day every week until the platelets had decreased to below 400 ! 10 9 /l. The average maintenance was 1.7 mg/day (range 1.0–2.5). Therapy was well tolerated. As ANA may interfere with platelet function [4] , the aspirin dose differed between HUand ANA-treated patients. The HU-treated patients received aspirin at a daily dose of 100 mg. The ANAtreated patients were on aspirin at a daily dose of 50 mg. Eleven out of 17 HU-treated patients (5 men, 6 women; mean age 68.6 years, range 27–87) developed thrombosis and included 6 episodes of transient ischemic attack, 3 episodes of acute myocardial infarct and 2 cases of deep venous thrombosis. The thrombosis occurred at a median time from diagnosis of 2 years. The ANA-treated patients did not experience thrombosis. Platelets were determined on the Sysmex XE-21300 (Dasit, Milan, Italy). PF4, F1 + 2, TAT, DD and vWF were measured by enzyme-linked immunosorbent and immunoturbidimetric assay, respectively (Diagnostica Stago, Boehringer MannThrombohemorrhagic risk typically characterizes the essential thrombocythemia (ET) [1] . The standard management includes hydroxyurea (HU) plus aspirin [2] . It has been demonstrated that ET patients receiving HU and antiaggregants show normal platelet count but still present platelet coagulant activation [3] . Anagrelide (ANA) is a platelet-lowering drug that inhibits platelet aggregation [4] . Therefore, we evaluated the platelet count and markers of platelet coagulant activation such as platelet factor 4 (PF4), prothrombin fragment 1 + 2 (F1 + 2), thrombin antithrombin complex (TAT) and D-dimer (DD) in ET patients randomly enrolled and selected to be treated with HU or with ANA in combination with aspirin depending on the patient’s age; informed consent was provided by all patients. Platelet activation causes an acquired von Willebrand factor (vWF) defect, which is a marker of hemorrhagic risk [5] . Thus, we also determined vWF. All measurements were performed before treatment and when complete response, defined as platelet count ! 400 ! 10 9 /l for more than 1 month, was achieved. Prolonged exposure to thrombocytosis is associated with thrombohemorrhagic risk [6] . Hence, we also investigated the cytoreduction time in HUand ANA-treated patients, respectively. The study comprised 36 patients (19 men, 17 women; mean age 65 years, range 27–87) with ET diagnosed according to the Polycythemia Vera Study Received: August 6, 2007 Accepted after revision: September 27, 2007 Published online: November 29, 2007

Vascular Endothelial Growth Factor and Thrombopoietin in Patients with Essential Thrombocythemia and Polycythemia vera and Thrombotic Complications

Accessible online at: www.karger.com/aha Patients with essential thrombocythemia (ET) and polycythemia vera (PV) are prone to thrombosis [1]. Thrombotic risk factors are age 160 years, thrombotic history and excessive thrombocytosis for ET, and age 160 years and thrombotic history for PV [1]. Attempts to relate platelet defects with thrombosis have been disappointing [1, 2]. Increases in vascular endothelial growth factor (VEGF) and thrombopoietin (TPO) were found in ET and PV [3, 4], and platelet activation was shown on VEGF and TPO stimulation [5, 6]. We studied the VEGF and TPO levels in 45 patients with ET and 25 patients with PV consecutively enrolled and followed up prospectively for thrombosis. The patients fulfilled the criteria of the Polycythemia Vera Study Group [7]. The mean age of the 45 ET and 25 PV patients was 61 and 64 years, respectively. Their mean duration of disease was 3.69 years. None had a history of thrombosis or splenomegaly. Most were on cytoreduction and antiplatelets. None had acquired thrombotic or inherited risk factors. Forty healthy individuals served as controls. Of 45 ET and 25 PV patients, 32 ET and 13 PV patients (45 cases) developed thrombosis, whereas 13 ET and 12 PV (25 cases) did not. Briefly, we observed 64% of thrombotic events, including minor and severe thrombosis (table 1). The thrombosis occurred at a median time from diagnosis of 2 years. The mean age of patients with and without thrombosis was 59 and 66 years, respectively. Platelets were determined by a Sysmex SF-3000 (Dasit, Milan, Italy). Plasma ß-thromboglobulin (ßTG) and platelet factor 4 (PF4), serum VEGF and plasma TPO were measured by ELISA (Diagnostica Stago Boehringer Mannheim, Germany; Quantikine Human Immunoassay, R&D Systems, Minneapolis, Minn., USA). Blood samples were collected at enrollment and at thrombosis. As VEGF and TPO elevation may be a consequence of thrombosis, we repeated these measurements in another sample collected 3 months after thrombosis. These measurements showed concordance for VEGF and TPO concentrations. Considering that VEGF may be produced by platelets [8], we adjusted VEGF per platelet (VEGFPLT/106). None had excessive thrombocytosis (521 B 259 ! 109/l) and all showed higher ßTG and PF4 (220 B 33 and 134 B 59 IU/ml, respectively) than controls (25 Table 1. Thrombotic events in 45 patients with ET and PV