Pegylated interferon for the treatment of high risk essential thrombocythemia: results of a phase II study.
OBJECTIVE
Patients with high-risk essential thrombocythemia require cytoreductive therapy in order to normalize the elevated platelet counts. We evaluated the efficacy and toxicity of pegylated interferon in high-risk essential thrombocythemia in a phase II trial.


METHODS
Thirty-six patients with high-risk essential thrombocythemia (median age 54 years; range, 24-72 years) were studied. The dose of pegylated interferon was initially 50 mg per week and could be escalated up to 150 mg per week.


RESULTS
During the first three months platelet counts decreased significantly from a median baseline count of 895x10(9)/L (range: 383-1779) to a median count of 485x10(9)/L (range: 211-1283; p<=0.001). A complete response was defined as platelet counts < 450x10(9)/L. The complete response rate was 39%, 47%, 58% and 67% at 3, 6, 9 and 12 months of treatment, respectively. There were 25%, 11%, 8% and 0% poor responders, defined as patients with platelet counts > 600x10(9)/L, at 3, 6, 9 and 12 months of treatment, respectively. After a median time of 23 months (range 3-39 months) 23 of 36 patients (64%) are still receiving pegylated interferon. In ten patients (28%) treatment was stopped due to grade 1 to 2 toxicity, classified according to the WHO standard toxicity scale. One patient, who responded partially to pegylated interferon (platelet count 542x10(9)/L), had a cerebral stroke after 23 months of treatment.


CONCLUSIONS
In high-risk essential thrombocythemia sustained treatment with pegylated interferon is effective and safe in reducing platelet counts with a toxicity comparable to that of conventional interferon.
Langer
Christian
C
Department of Medicine III, University of Ulm, Germany.
Lengfelder
Eva
E
Thiele
Jürgen
J
Kvasnicka
Hans M
HM
Pahl
Heike L
HL
Beneke
Heimo
H
Schauer
Stefanie
S
Gisslinger
Heinz
H
Griesshammer
Martin
M
D000328:Adult; D000368:Aged; D017322:Clinical Trials, Phase II as Topic; D005260:Female; D006801:Humans; D000077190:Interferon alpha-2; D016898:Interferon-alpha / Q000009:adverse effects / Q000627:therapeutic use*; D008297:Male; D008875:Middle Aged; D010976:Platelet Count; D011092:Polyethylene Glycols / Q000009:adverse effects / Q000627:therapeutic use*; D011994:Recombinant Proteins; D012307:Risk Factors; D013920:Thrombocythemia, Essential / Q000097:blood / Q000188:drug therapy*
D000077190:Interferon alpha-2; D016898:Interferon-alpha; D011994:Recombinant Proteins; D011092:Polyethylene Glycols; C100416:peginterferon alfa-2a