Combination therapy of hydroxycarbamide with anagrelide in patients with essential thrombocythemia in the evaluation of Xagrid(R) efficacy and long-term safety study.

Available information is limited regarding the use of cytoreductive combination therapy in high-risk patients with essential thrombocythemia. This analysis aims to evaluate the clinical relevance and patterns of cytoreductive combination treatment in European high-risk patients with essential thrombocythemia in the Evaluation of Xagrid (R) Efficacy and Long-term Safety study. Of 3643 patients, 347 (9.5%) received combination therapy. Data were recorded at each 6-month update. Of 347 patients who received combination therapy, 304 (87.6%) received hydroxycarbamide + anagrelide. Monotherapies received before this combination were hydroxycarbamide (n=167, 54.9%) and anagrelide (n=123, 40.5%). Median weekly doses of hydroxycarbamide and anagrelide were: 7000 and 10.5 mg when used as prior monotherapy; 3500 and 7.0 mg when used as add-on treatment. Overall, median platelet counts were 581x10(9)/L and 411x10(9)/L before and after starting hydroxycarbamide + anagrelide, respectively. In patients with paired data (n=153), the number of patients with platelet counts less than 400x10(9)/L increased from 33 (21.6%) to 74 (48.4%; P<0.0001), and with platelet counts less than 600x10(9)/L, from 82 (53.6%) to 132 (86.3%; P<0.0001). Hydroxycarbamide + anagrelide was discontinued in 158 patients: 76 (48.1%) stopped hydroxycarbamide, 59 (37.3%) stopped anagrelide, 19 (12.0%) stopped both and 4 (2.5%) had another therapy added. The most frequent reasons for discontinuation were intolerance/side-effects, lack of efficacy, and therapeutic strategy. Combination therapy, usually hydroxycarbamide + anagrelide, is used in approximately 10% of all high-risk patients with essential thrombocythemia and may be a useful approach in treating patients for whom monotherapy is unsatisfactory.