Disparities of cost-sharing subsidies among Medicare beneficiaries with chronic myeloid leukemia (CML) may reduce adherence to tyrosine kinase inhibitor (TKI) therapy, according to a study published in the Journal of Clinical Oncology.1

TKIs have dramatically increased the life expectancy among patients with CML. For some patients, however, these drugs are prohibitively expensive, which can lead to a delay in treatment initiation. High prescription costs may also reduce adherence; both low adherence and delays in treatment initiation are both linked to worse survival.

Researchers enrolled 393 patients at least 66 years old (one must be at least 65 to enroll in Medicare) who were diagnosed with CML between 2007 and 2011. Only 68.2% of patients initiated TKI therapy within 6 months of diagnosis; only 61% of those who initiated TKI therapy were adherent for 6 months after initiating therapy.

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Living in a large metropolitan area and being younger than 70 raised the likelihood of TKI initiation; those older than 80 were also less likely to adhere to medication regimens than those younger than 70. Patients with cost-sharing subsidies were likely to initiate therapy sooner than those without.

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The authors conclude that there are gaps in TKI initiation and adherence among Medicare-enrolled patients with CML. Patients without cost-sharing subsidies may pay almost $3000 for the first month of TKI therapy, followed by $550 per month for the rest of the year. These high costs may lead to earlier mortality due to suboptimal rates of drug initiation and adherence.


  1. Winn AN, Keating NL, Dusetzina SB. Factors associated with tyrosine kinase inhibitor initiation and adherence among Medicare beneficiaries with chronic myeloid leukemia. J Clin Oncol. 2016 Oct 3. doi: 10.1200/JCO.2016.67.4184 [Epub ahead of print]