Long term molecular responses in a cohort of Danish patients with essential thrombocythemia, polycythemia vera and myelofibrosis treated with recombinant interferon alpha

Abstract

Within recent years data has accumulated demonstrating the efficacy of recombinant interferon alpha2 (rIFN-alpha2) in the treatment of chronic myeloproliferative neoplasms (MPNs). We report on clinical and molecular data in the largest cohort of JAK2 V617F mutant MPN Danish patients (n=102) being treated long-term with rIFN-alpha2 (rIFN-alpha2a and rIFN-alpha2b in a non-clinical trial setting. The median follow-up was 42 months. We substantiate the capacity of rIFN-alpha2 to induce complete hematologic remissions (ET 95%, PV 68%) and molecular response. In total 76 patients (74.5%) had a decline in JAK2 V617F allele burden with a median reduction from baseline of 59% (95% c.i. 50-73%, range 3-99%). A decline in JAK2 V617F allele burden was recorded in both ET (median 24-10% (95% c.i.: 8-16%), and PV (median 59-35% (95% c.i.: 17-33%). Patients with the lowest pre-treatment JAK2 V617F allele burdens tend to achieve the most favourable responses on long term treatment with rIFN-alpha2. Eleven patients (10%) had deep molecular remissions with ≤ 2% JAK2 V617F mutant DNA. Finally, long term treatment with rIFN-alpha2 was associated with a very low thrombosis rate. Our observations are supportive of the concept of early up-front treatment with rIFN-alpha2.