Tolerability and Efficacy of Pegylated Interferon-α-2a in Combination With Imatinib for Patients With Chronic-Phase Chronic Myeloid Leukemia

BACKGROUND: The pegylated form of interferon--2a (PegIFNa2a) in combination with imatinib has demonstrated a molecular improvement in patients with chronic-phase chronic myeloid leukemia. However, to the authors' knowledge, the appropriate dose of PegIFNa2a has not been established to date. METHODSIn the French SPIRIT trial, the authors compared 2 initial doses of PegIFNa2a, taking into account an amendment that recommended reducing that dose from 90 g/week to 45 g/week because of toxicities. Accordingly, 2 subgroups of patients were identified: the PegIFN90 group (171 patients who were treated with the 90-g/week dose) and the PegIFN45 group (50 patients who were treated with the 45-g/week dose). Both groups were compared for toxicity and efficacy. RESULTSPegIFNa2a at a dose of 90 g/week resulted in a rate of 54% of grade 3 to 4 hematologic toxicity compared with 27% with the dose of 45 g/week (P<.001), leading to discontinuation rates of 40% and 10%, respectively, before 6 months. The dose reduction did not significantly affect the efficacy of the combination. By 12 months, the cumulative molecular response rates (ie, BCR-ABL/abl0.01 [IS: molecular responses graded as molecular response 4 (MR4)]) were 14% and 25%, respectively, for the subgroup treated with imatinib at a dose of 400 mg and the PegIFN90 subgroup. After the amendment, the MR4 rates were 10% and 28%, respectively, for the subgroup treated with imatinib at the 400-mg dose and PegIFN45 subgroup (P<.0001). CONCLUSIONSThe results of the current study demonstrate that in combination with imatinib, the efficient dose of PegIFNa2a appears to be 45 g/week. Cancer 2013;119:4284-4289. (c) 2013 American Cancer Society.