Long-term follow-up of essential thrombocythemia patients treated with anagrelide: subgroup analysis according to JAK2/CALR/MPL mutational status

BackgroundAnagrelide represents a treatment option for essential thrombocythemia, although its place in therapy remains controversial. AimTo assess the impact of mutational status in response rates and development of adverse events during long-term use of anagrelide. MethodsWe retrospectively evaluated 67 patients with essential thrombocythemia treated with anagrelide during 68 (4-176) months. ResultsMutational frequencies were 46.3%, 28.3%, and 1.5% for JAK2V617F, CALR and MPL mutations. Anagrelide yielded a high rate of hematologic responses, which were complete in 49.25% and partial in 46.25%, without differences among molecular subsets. The rate of thrombosis during treatment was one per 100 patient-years, without excess bleeding. Anemia was the major adverse event, 30.3% at 5-yr follow-up, being more frequent in CALR (+) (P<0.05). Myelofibrotic transformation developed in 14.9% (12.9%, 21%, and 12.5% in JAK2V617F(+), CALR (+), and triple-negative patients, respectively, P=NS) and those treated >60months were at higher risk, OR (95% CI) 9.32 (1.1-78.5), P<0.01, indicating the need for bone marrow monitoring during prolonged treatment. ConclusionAlthough CALR (+) patients were at higher risk of developing anemia, anagrelide proved effective among all molecular subsets, indicating that mutational status does not seem to represent a major determinant of choice of cytoreductive treatment among essential thrombocythemia therapies.