Should Chemotherapy Be Administered for Essential Thrombocythemia (ET) Patients with Leukemic Transformation?

Abstract

Introduction: Essential Thrombocythemia (ET) is a clonal myeloproliferative disease presenting predominantly with thrombocytosis. One of its rare complications is leukemic transformation (LT). Once leukemic transformation occurs, prognosis is dismal. We aim to determine the disease profile of LT in our ET patients and evaluate if chemotherapy can alter prognosis. Methods: Clinical data of all patients diagnosed and treated with ET from 1999 to 2008 in the Department of Hematology, Singapore General Hospital, were captured in the Myeloproliferative Disease(MPD) Registry. ET patients with LT were selected. Patient characteristics, disease profile, including ET treatment, duration from ET diagnosis to LT, prior myelofibrosis (MF) history, type of chemotherapy, response and eventual survival were recorded. Results: Two hundred and thirty ET patients were diagnosed and treated from 1999 to 2008. Six patients had LT (2.6%). All were Chinese. Four were females. Age range was 47–70 years (mean 61.2 years). Transformation to acute myeloid leukemia (AML) was seen in 5 patients, after a latency period of 3–28 years. Acute biphenotypic leukemia was diagnosed in 1 patient 4 years after ET diagnosis. All patients had received hydroxyurea. There was no prior evolution to MF. Complex cytogenetics were seen in all cases. Three patients treated conservatively died within 1 month. The other 3 patients did not go into durable complete remission despite chemotherapy and succumbed within 9 months. Conclusions: Leukemic transformation in ET, though rare, is associated with grave prognosis. Outcome with chemotherapy is dismal. More studies are needed to evaluate if alternative treatment can improve survival.