Clinical Features of Polycythemia Vera and Essential Thrombocythemia in Japan: Retrospective Analysis of a Nationwide Survey by the Japanese Elderly Leukemia and Lymphoma Study Group

Abstract

We conducted the first nationwide survey to clarify the clinical features, treatment methods, and prognoses for polycythemia vera (PV) and essential thrombocythemia (ET). A 1-page questionnaire was mailed to members of the Japanese Elderly Leukemia and Lymphoma Study Group (JELLSG). Surveys on 647 patients (PV, 266 patients; ET, 381 patients) were returned and analyzed. Thrombotic events at diagnosis and during follow-up occurred at rates of 15.4% and 8.5%, respectively, in PV cases and 17.6% and 8.7% in ET cases. Splenomegaly was observed in only 28.8% of PV patients and 10.8% of ET patients. The leukocyte alkaline phosphatase score was elevated in only 46.2% of PV patients. The incidences of abnormal karyotypes were less than 10% in both PV and ET cases. The rates of transformation to myelofibrosis were 2.6% in both PV and ET cases, and acute leukemia was noted in 1.1% of PV patients and 2.9% of ET patients. Prognostic factors were thrombotic history for PV and thrombotic history and age (>or=60 years) for ET. The present study clearly demonstrated clinical differences between Japanese and Western patients for PV and ET. Concerning the treatment of PV and ET, the study revealed considerable variation among Japanese hematologists. These results suggest the necessity of developing treatment guidelines according to risk stratification that are suitable for Japanese PV and ET patients.

Prognostic factors for thrombosis, myelofibrosis, and leukemia in essential thrombocythemia: a study of 605 patients

“…40 Concerning the potential role of cytotoxic agents in the development of leukemia, prior studies reported that hydroxy-urea may be leukemogenic, 19,41 and that the use of more than one cytotoxic agent may increase the risk of leukemic transformation. 4,42 However, leukemia may develop in patients who have never received cytotoxic drugs, 43 and large studies did not show that cytotoxic agents were involved in leukemic transformation. [3][4][5] Our results indicate that the risk of leukemia increases over time and that patients treated with cytotoxic agents do not have a significantly different risk of leukemic transformation compared to that of patients receiving antiplatelet agents alone.…”

Phase III, single-arm study investigating the efficacy, safety, and tolerability of anagrelide as a second-line treatment in high-risk Japanese patients with essential thrombocythemia

“…Hydroxycarbamide (HC) is the most widely used CRT for ET in Japan [4]. It has been suggested that long-term HC use is associated with a higher incidence of secondary leukemia [5].…”

Risk stratification for survival and leukemic transformation in essential thrombocythemia: a single institutional study of 605 patients

“…7,8 In contrast to this scenario regarding thrombosis in ET, the pertinent literature reveals a considerable degree of inconsistency regarding life expectancy and the incidence of LT and its relationship to drug therapy. 1,[9][10][11][12][13][14][15][16][17][18][19] One major factor that contributes to the discrepancy in reported figures concerning survival and LT in ET is the small number of events and their dependence on time that necessitates both large sample size and long-term follow-up. Another factor that is often overlooked is the possibility of interstudy differences in risk distribution of the study population that arise from diagnostic imprecision and referral bias, 20,21 among other things.…”