Interferon alpha-2c therapy of patients with chronic myelogenous leukemia: long-term results of a multicenter phase-II study
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In a prospective multicenter phase-II trial 80 patients with Philadelphia (Ph)-positive chronic myelogenous leukemia (CML) were treated with recombinant interferon (IFN)α-2c, administered subcutaneously at an absolute dose of 3.5 megaunits (MU)/day. Complete hematological remission was achieved in 29 (39%) and partial hematological remission in 26 (35%) of the 74 patients evaluable for response. Major cytogenetic responses were observed in ten (13%) and minor cytogenetic responses in 11 patients (15%). Median duration of cytogenetic response was 33 months (range, 2–90); relapses were seen in all of the 11 patients with minor and in three of the ten patients with major cytogenetic responses. Median survival estimates for pretreated (n=19) and untreated (n=58) patients were 51 months (95% confidence interval [CI], 30–72) and 77 months (95% CI, 43–111), and the survival probabilities at 5 years were 45% and 54% for the two groups, respectively. Hematological response after 3 months of treatment demonstrated a clear-cut discriminative capacity with 5-year survival probabilities of 100%, 67% and 24% for patients achieving CHR (n=6), PHR (n=34), and less than PHR (n=35), respectively. Landmark analysis at 12, 18, and 24 months after start of IFN therapy and an analysis treating time to cytogenetic response as a time-dependent covariate showed that cytogenetic response was associated with longer survival. The impact of a low-dose IFN regimen on survival in CML patients is unclear and requires further clarification by randomized clinical trials. Early hematological and cytogenetic response to IFN-α treatment identifies patients with a favorable long-term prognosis.
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