Updated Estimates of Survival and Cost Effectiveness for Imatinib versus Interferon-alpha Plus Low-Dose Cytarabine for Newly Diagnosed Chronic-Phase Chronic Myeloid Leukaemia

Background: For trials in which participants are followed beyond the main study period to assess long-term outcomes, economic evaluations conducted using short-term data should be systematically updated to reflect new information. Methods: We used 60-month survival data from the IRIS (International Randomized study of Interferon vs STI571) trial to update previously published cost-effectiveness estimates, based on 19 months of follow-up, of imatinib versus interferon (IFN)-alpha plus low-dose cytarabine in patients with chronic-phase chronic myeloid leukaemia. For patients treated with imatinib, we used the 60-month data to calibrate the survival curves generated from the original cost-effectiveness model. We used historical data to model survival for patients randomized to IFNalpha. We updated costs for medical resources using 2006 Medicare reimbursement rates and applied average wholesale prices (AWPs) and wholesale acquisition costs (WACs) to study medications. Results: Five-year survival for patients randomized to imatinib was better than predicted in the original model (89.4% vs 83.2%). We estimated remaining life expectancy with first-line imatinib to be 19.1 life-years (3.8 life-years over the original model) and 15.2 QALYs (3.1 QALYs over the original estimate). Estimates for IFNalpha remained at 9.1 life-years and 6.3 QALYs. When we applied AWPs to study medications, incremental cost-effectiveness ratios (ICERs) were $US51_800-57_500 per QALY. When we applied WACs, ICERs were $US42_000-46_200 per QALY. Conclusion: Although the analysis revealed that the original survival estimates were conservative, the updated cost-effectiveness ratios were consistent with, or slightly higher than, the original estimates, depending on the method for assigning costs to study medications.