Tolerability and efficacy of pegylated interferon-α-2a in combination with imatinib for patients with chronic-phase chronic myeloid leukemia.

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BACKGROUND: The pegylated form of interferon-α-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. METHODS: In the French SPIRIT trial, the authors compared 2 initial doses of PegIFNa2a, taking into account an amendment that recommended reducing that dose from 90 μg/week to 45 μg/week because of toxicities. Accordingly, 2 subgroups of patients were identified: the PegIFN90 group (171 patients who were treated with the 90-μg/week dose) and the PegIFN45 group (50 patients who were treated with the 45-μg/week dose). Both groups were compared for toxicity and efficacy. RESULTS: PegIFNa2a at a dose of 90 μg/week resulted in a rate of 54% of grade 3 to 4 hematologic toxicity compared with 27% with the dose of 45 μg/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/abl ≤ 0.01 [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). CONCLUSIONS: The results of the current study demonstrate that in combination with imatinib, the efficient dose of PegIFNa2a appears to be 45 μg/week. Society.

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