Purpose: The introduction of imatinib, a tyrosine kinase inhibitor (TKI), has greatly increased survival for patients with chronic myeloid leukemia (CML). Conversely, nonadherence to imatinib and other TKIs undoubtedly results in disease progression and treatment resistance. We examined trends in imatinib expenditures from 2002 to 2011 and assessed the association between copayment requirements for imatinib and TKI adherence.
Patients and methods: We used MarketScan health plan claims from 2002 to 2011 to identify adults (age 18 to 64 years) with CML who initiated imatinib therapy between January 1, 2002, and June 30, 2011, and had insurance coverage for at least 3 months before through 6 months after initiation (N = 1,541). Primary outcomes were TKI discontinuation and nonadherence. The primary independent variable was out-of-pocket cost for a 30-day supply of imatinib. By using a propensity-score weighted sample, we estimated the risk of discontinuation and nonadherence for patients with higher (top quartile) versus lower copayments.
Results: Monthly copayments for imatinib averaged $108; median copayments were $30 (range, $0 to $4,792). Mean total monthly expenditures for imatinib nearly doubled between 2002 and 2011, from $2,798 to $4,892. Approximately 17% of patients with higher copayments and 10% with lower copayments discontinued TKIs during the first 180 days following initiation (adjusted risk ratio [aRR], 1.70; 95% CI, 1.30 to 2.22). Similarly, patients with higher copayments were 42% more likely to be nonadherent (aRR, 1.42; 95% CI, 1.19 to 1.69).
Conclusion: Patients with higher copayments are more likely to discontinue or be nonadherent to TKIs. Given the importance of these therapies for patients with CML, our data suggest a critical need to reduce patient costs for these therapies.