Anagrelide in Essential Thrombocythemia (ET): Results from 150 patients over 25 years by the “Ph1‐negative Myeloproliferative Neoplasms Latium Group”

The Italian Society of Hematology (SIE) and the two affiliated Societies (SIES and GITMO) commissioned a project to develop guidelines for the therapy of essential thrombocythemia (ET) using evidence-based knowledge and consensus formation techniques. Key questions on the optimal management of ET patients were formulated by an Advisory Council (AC) and approved by an Expert Panel (EP) composed of 7 senior hematologists. The AC systematically reviewed the published literature from 1980 to August 2002, and articles were graded according to their internal validity and quality. Using the Delphi technique, the EP was asked to answer the key questions according to the available evidence. From September 2002 to March 2003, four Consensus Conferences were held in accordance with the Nominal Group Technique with the goal of solving residual disagreement on recommendations. The EP provided recommendations on when to start platelet-lowering therapy, the most appropriate platelet-lowering agent, the use of anti-platelet therapy, and the management of women in childbearing age and of pregnant women. By using evidence and consensus, recommendations for the treatment of key problems in ET have been issued. Statements are graded according to the strength of the supporting evidence and uncertainty is explicitly declared.

Although anagrelide is widely used in the treatment of thrombocythemia in myeloproliferative diseases, there is currently limited information on the efficacy and toxicity of its long-term use. This prospective study investigated clinical toxicity and efficacy of anagrelide during two years of treatment. A multicenter, open, phase II study of anagrelide treatment was performed by the Swedish Myeloproliferative Disorder Study Group. The study included 60 patients with thrombocythemia due to myeloproliferative disease, 42 with essential thrombocythemia (ET), 17 with polycythemia vera (PV) and one with myelofibrosis (MF). Complete response (CR), defined as a platelet count 9 at 24 months. After two years, 50% (n=30) of the patients continued anagrelide treatment. Side effects and toxic discontinuation rates were higher than in previous studies, probably because this is the first long-term prospective study of the feasibility and toxicity of anagrelide treatment. Nevertheless, anagrelide is a valuable alternative for treatment of thrombocythemia in myeloproliferative disorders for patients who tolerate the drug well.

Essential thrombocythemia (ET) can be complicated by life-threatening thrombosis and has a risk of converting into acute leukemia. Cytoreductive therapy may reduce the risk of thromboembolic complications. Herein, we report the results of a long-term study of patients with ET treated with anagrelide to control thrombocytosis. Thirty-nine (34 evaluable) patients (median age, 33 years; 24 previously untreated) were enrolled between 1989-1996; the mean platelet count prior to therapy was 1197x10(9)/L. Only 9 out of 34 evaluable patients were at high risk of thrombosis (platelet count more than 1500x10(9)/L). The initial dose of anagrelide (0.5 mg/bid for 7 days) was increased by 0.5 mg/day (maximum dose: 3 mg/day) until a response was seen. A complete response (platelets 1 month) was seen in 15 /34 (44%) patients and a partial response (platelets 450-600x10(9)/L for >1 month) was seen in 17/34 ( 50%), so that the some kind of response was seen in 32/34 (94%) of the patients at a median time of 4.2 months after starting treatment. Seventeen patients (50%) are still being treated and have achieved platelet control for a maximum follow-up of 12.5 years. Late onset anemia occurred in 4/39 patients. Three out of 39 patients (8%) had cardiac disorders. Anagrelide appears suitable for controlling thrombocytosis in ET patients over the long-term. This drug may be used in patients younger than 60 years, with the exclusion of women of child-bearing potential and subjects aged 40-60 years with a history of major thrombotic events. Anagrelide should not be administered to patients with cardiac disorders, and a careful approach to patients should include monitoring of heart function before and during treatment.