Long-term outcome of 231 patients with essential thrombocythemia: prognostic factors for thrombosis, bleeding, myelofibrosis, and leukemia.
BACKGROUND
Essential thrombocythemia (ET) is a clonal myeloproliferative disease associated with thrombohemorrhagic complications and myeloid transformation to diseases such as myelofibrosis and acute myeloid leukemia.


METHODS
A multicenter study was conducted among 231 consecutive Chinese patients with ET. The literature about leukemogenic risk associated with the use of hydroxyurea therapy was reviewed.


RESULTS
The median patient age was 65 years. Thrombosis rates at and after diagnosis of ET were comparable to those of white patients, but bleeding rates at and after diagnosis were much lower. The projected 10-year thrombosis-free, bleeding-free, and overall survival rates were 66%, 83%, and 80%, respectively. There were no deaths among patients 60 years or younger during a maximum follow-up of 15 years, and splenomegaly at diagnosis of ET appeared to protect against thrombosis. In multivariate analysis, advanced age predicted inferior 10-year thrombosis-free and overall survival, and male sex predicted inferior bleeding-free survival. Half the deaths were related to ET. The probability of myelofibrosis transformation was 9.7% at 10 years. Prior myelofibrosis (P = .008) and the use of melphalan treatment (P = .002) were risk factors for acute myeloid leukemia evolution.


CONCLUSIONS
Essential thrombocythemia is a benign disease of older persons. Chinese patients have a low risk of bleeding, and prior myelofibrosis is a major risk factor for evolution to acute myeloid leukemia. Leukemic transformation with hydroxyurea therapy alone is rare and warrants further prospective studies.
Chim
Chor-Sang
CS
Department of Medicine, Queen Mary Hospital, University of Hong Kong, 102 Pokfulam Road, Hong Kong, ROC. jcschim@hkucc.hku.hk
Kwong
Yok-Lam
YL
Lie
Albert Kwok-Wei
AK
Ma
Siu-Kwan
SK
Chan
Chi-Chung
CC
Wong
Lap-Gate
LG
Kho
Bonnie Chi San
BC
Lee
Harold-Kwok
HK
Sim
Joycelyn Pui-Yin
JP
Chan
Cheuk-Hung
CH
Chan
Joyce Chee-Wun
JC
Yeung
Yiu-Ming
YM
Law
Martin
M
Liang
Raymond
R
D000208:Acute Disease; D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D000970:Antineoplastic Agents / Q000627:therapeutic use; D044466:Asian People; D002471:Cell Transformation, Neoplastic; D005260:Female; D005500:Follow-Up Studies; D006723:Hong Kong / Q000453:epidemiology; D006801:Humans; D006918:Hydroxyurea / Q000627:therapeutic use; D007951:Leukemia, Myeloid / Q000453:epidemiology* / Q000473:pathology; D008297:Male; D008558:Melphalan / Q000627:therapeutic use; D008875:Middle Aged; D015999:Multivariate Analysis; D019653:Myeloablative Agonists / Q000627:therapeutic use; D055728:Primary Myelofibrosis / Q000453:epidemiology*; D011379:Prognosis; D012307:Risk Factors; D012737:Sex Factors; D013163:Splenomegaly; D016019:Survival Analysis; D013920:Thrombocythemia, Essential / Q000150:complications / Q000188:drug therapy / Q000401:mortality*; D013927:Thrombosis / Q000453:epidemiology*; D017086:beta-Thalassemia / Q000453:epidemiology
D000970:Antineoplastic Agents; D019653:Myeloablative Agonists; D008558:Melphalan; D006918:Hydroxyurea