Imatinib in patients with newly diagnosed chronic-phase chronic myeloid leukemia.

The International Randomized Study of Interferon and STI571 (IRIS) study prospectively compared imatinib with interferon-alpha/low-dose cytarabine (IFN/LDAC) in 1,106 newly diagnosed patients with Philadelphia chromosome-positive chronic myeloid leukemia (CML). Patients not responding to or intolerant of their assigned treatment were allowed to cross over. At 18 months, the projected probability of achieving a complete cytogenetic response was 76.2% for imatinib and 14.5% for IFN/LDAC, respectively (P <.01). Freedom from progression to accelerated phase or blast crisis was 96.7% for imatinib versus 91.5% for IFN/LDAC (P <.01). At the time of the analysis, 85.7% of imatinib-treated patients continued on first-line therapy, but only 10.8% of patients continued with IFN/LDAC. Most cross-overs to imatinib were due to interferon-intolerance. Overall survival was not different in the two groups at 19 months, reflecting efficient rescue of IFN/LDAC failures with imatinib. Imatinib should now be considered the standard therapy for newly diagnosed patients with CML.