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14. Non-Leukemic Chronic Myeloproliferative Disorders
14.3 Essential thrombocythemia (ET)
14.3.1. General considerations
The defining characteristic of essential thrombocythemia (ET) is a sustained elevation of the platelet count above 600000/µl in the untreated patient. Clinically ET is characterized by vasomotor symptoms , thrombohemorrhagic complications, recurrent fetal loss, and tranformation into either chronic idiopathic mylofibrosis (myelofibrosis with myeloid metaplasia ) or acute myeloid leukemia.
About one third of patients are asymptomatic at diagnosis and, untreated, may often remain without complications for years. Present treatment of those patients requiring intervention is a compromise between prevention of ET-related thrombotic and bleeding complications on one hand and avoidance of long-term toxicity on the other hand .
Cytoreduction with hydroxyurea has emerged as the treatment of choice for patients with a a high risk of thrombosis . Because of some concern regarding its potential role in enhancing the risk of leukemic transformation. Hydroxyurea is no longer recommended in young patients at low risk for thrombosis . The more recent availability of nonmutagenic drugs like interferon alpha and anagrelide and the recognition of the role of antiaggregating agents like aspirin in the treatment of microvascular ischemic events has broadened the therapeutic options. Preliminary data indicate that high-dose chemotherapy with hematopoietic stem cell transplantation might be curative for selected patients with advanced disease.
Literature: for review e.g.
BRIERE and GUILMIN, Pathol. Biol. 49 (2001): 178-183
GRIESSHAMMER et al, Exp. Opin. Pharmacother. 2 (2001): 385 – 393
PLATZBECKER et al, Leuk, Lymphoma 43 (2002): 1409 – 1414
(hematopoietic stem cell transplantation)
SOLBERG, Semin. Oncol. 29 (Suppl 10 ) (2002): 10 – 15
TEFFERI, Leuk Res. 25 (2001): 369 – 377
TEFFERI and MURPHY, Blood Rev. 15 (2001): 121 – 131
14.3.2. Hydroxyurea
|
Hydroxyurea usually 500 mg p.o. 2 – 3 times daily |
Literature :
FINAZZI and BARBUI, Pathol. Biol. 49 (2001): 167 – 169
FINAZZI et al, Br. J. Haematol. 110 (2000): 577 – 583
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14.3.3. Anagrelide
|
Anagrelide initial dose 0.5 mg p.o. 4 times daily or 1.0 mg p.o. 2 times daily which should be maintained for at least 1 wk. Dosage should then be adjusted to maintain platelet count below 600000/mI |
Literature:
BROOKS et al, Ann, Pharmacother, 33 (1999): 1116 – 1118 , 1121
OERTEL, Am. J. Health , Syst. Pharm. 55 (1998): 1979 – 1986
SILVERSTEIN and TEFFERI, Semin, Hematol. 36 (Suppl 2) (1999):23 – 25
STOREN and TEFFERI, Blood 97 (2001): 863 – 866
14.3.4 Interferon alpha
|
Interferon alpha e.g. 3 x 10 6 IU s.c. 3 x weekly |
Literature:
LENGFELDER et al, Leuk. Lymphoma 22 (Suppl) (1996): 1135 – 1142