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. Cancer 2013;119:4284–4289. © 2013 American Cancer Society.