Objectives: In chronic myeloid leukemia, after promising results in major cytogenetic remission (MCR), long-term survival data on imatinib treatment is of particular interest, especially in relation to former standard treatment based on interferon-alpha. However, data is still unavailable and due to high remission rates, most patients randomized to interferon-alpha in a clinical trial crossed over to imatinib. Therefore, to assess the expected long-term survival advantage with imatinib, a simulation study based on prognostic factors validated for interferon-alpha treatment was performed.
Methods: In interferon-alpha-treated patients with intermediate-risk and low-risk according to the established New CML score, survival probabilities of patients with MCR were significantly higher than those of patients without MCR. Three samples with simulated survival data for imatinib-treated intermediate-risk patients were constituted by randomly drawing varying percentages of their survival times from interferon-alpha-treated intermediate-risk patients with MCR and the remaining data from intermediate-risk patients without MCR. The same procedure was applied to low-risk patients.
Results: The 10-year survival probabilities of inter-feron-alpha-treated intermediate-risk and low-risk patients were 0.22 and 0.37. In the simulated samples, when 80%, 65%, and 50% of survival times were as favorable as for interferon-alpha-treated patients with MCR, respectively, the corresponding survival probabilities were 0.43 and 0.57, 0.36 and 0.49, and 0.30 and 0.42.
Conclusions: In all simulation samples, increments of survival probabilities by imatinib were predicted, although survival probabilities of patients with MCR were assumed to be lower than with interferon-alpha. Prognosticated survival advantage with imatinib is backed by increasing observation time of imatinib-treated patients in real studies.