Originally published as JCO Early Release 10.1200/JCO.2009.23.6075 on October 13 2009

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Pegylated Interferon Alfa-2a Yields High Rates of Hematologic and Molecular Response in Patients With Advanced Essential Thrombocythemia and Polycythemia Vera

From the Departments of Leukemia and Hematopathology, The University of Texas M. D. Anderson Cancer Center, Houston, TX.

Corresponding author: Srdan Verstovsek, MD, PhD, The University of Texas M. D. Anderson Cancer Center, Department of Leukemia, Unit 428, 1515 Holcombe Blvd, Houston, TX 77030; e-mail: sverstov{at}mdanderson.org.

Purpose We conducted a phase II study of pegylated interferon alfa-2a (PEG-IFN--2a) in patients with essential thrombocythemia (ET) and polycythemia vera (PV).

Patients and Methods Seventy-nine patients (40 with PV and 39 with ET) have been treated. Median time from diagnosis to PEG-IFN--2a was 54 months in patients with PV and 33 months in patients with ET. Eighty-one percent of patients had received prior therapy. The first three patients received PEG-IFN--2a at 450 µg weekly. As a result of poor tolerance, this dose was decreased in a stepwise manner to a current starting dose of 90 µg weekly. Seventy-seven patients are evaluable and have been observed for a median of 21 months.

Results The overall hematologic response rate was 80% in PV and 81% in ET (complete in 70% and 76% of patients, respectively). The JAK2^V617F mutation was detected in 18 patients with ET and 38 patients with PV; sequential measurements by a pyrosequencing assay were available in 16 patients with ET and 35 patients with PV. The molecular response rate was 38% in ET and 54% in PV, being complete (undetectable JAK2^V617F) in 6% and 14%, respectively. The JAK2^V617F mutant allele burden continued to decrease with no clear evidence for a plateau. The tolerability of PEG-IFN--2a at 90 µg weekly was excellent.

Conclusion PEG-IFN--2a resulted in remarkable clinical activity, high rates of molecular response, and acceptable toxicity in patients with advanced ET or PV. The ability of PEG-IFN--2a to induce complete molecular responses suggests selective targeting of the malignant clone.

Authors' disclosures of potential conflicts of interest and author contributions are found at the end of this article.

Clinical trial information can be found for the following: NCT00452023 [ClinicalTrials.gov] .

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