Adherence to tyrosine kinase inhibitors among Medicare Part D beneficiaries with chronic myeloid leukemia

BACKGROUND

Tyrosine kinase inhibitors (TKIs) improve the survival of patients with chronic myeloid leukemia (CML) dramatically; however, nonadherence to TKI therapy may lead to resistance to the therapy. TKIs are very expensive and are covered under Part D insurance for Medicare patients. To the authors' knowledge, the impact of low-income subsidy status and cost sharing on adherence among this group has not been well studied in the literature.

METHODS

Surveillance, Epidemiology, and End Results (SEER) registry data linked with Medicare Part D data from the years 2007 through 2012 were used in the current study. The authors identified 836 patients with CML with Medicare Part D insurance coverage who were new TKI users. Treatment nonadherence was defined as a binary variable indicating the percentage of days covered was <80% during the 180-day period after the initiation of TKI therapy. Logistic regression was used to examine the relationship between out-of-pocket costs per 30-day drug supply, Medicare Part D plan characteristics, and treatment adherence while controlling for other patient characteristics.

RESULTS

Overall, 244 of the 836 patients with CML (29%) were nonadherent to targeted oral therapy during the 180 days after the initiation of treatment with TKIs. The multivariable logistic regression demonstrated that patients with heavily subsidized (odds ratio, 6.7; 95% confidence interval, 2.8-15.9) and moderately subsidized (odds ratio, 3.0; 95% confidence interval, 1.4-6.5) Medicare Part D plans were much more likely to demonstrate nonadherence compared with patients without a subsidy.

CONCLUSIONS

The current population-based study found a significantly higher rate of nonadherence among heavily subsidized patients with substantially lower out-of-pocket costs, which suggests that future research is needed to help lower the nonadherence rate among these individuals. Cancer 2018;124:364-73. © 2017 American Cancer Society.

Improving adherence to oral cancer therapy in clinical practice

Adherence to oral chemotherapy regimens maximizes their effectiveness and minimizes any potential toxicities. Factors specifically related to the treatment, patient, and health care provider may influence medication adherence. Treatment-related factors include the complexity of the regimen, the cost of therapy, the possibility of side effects, and the delay in treatment benefits. Meanwhile, patients may not have an adequate support system or an understanding of the need for the medication, and providers may not fully succeed in communicating the importance of adherence and the types of side effects that may occur. Nonadherence may lead to an increased risk of toxicity, decreased effectiveness, and increased utilization of health care resources. Although various methods for measuring adherence are available, self-reporting is the most widely used. Studies describing adherence in a broad range of cancers are reviewed. Treatment of chronic myeloid leukemia has been revolutionized by the development of oral tyrosine kinase inhibitors that are highly effective in managing the disease when taken consistently. However, nonadherence is relatively common and can lead to reduced rates of response and increased medical costs. Similar effects of nonadherence on outcome and cost have also been observed in patients with various other hematologic malignancies and solid tumors. Interventions to improve adherence to oral chemotherapy regimens include communication about the importance of adherence and the potential consequences of nonadherence, simplification of the patient's medication schedule (if possible), and inclusion of a caregiver or family member in the conversation. Written materials should always be provided to accompany verbal instructions. This review summarizes factors influencing medication adherence, impact of nonadherence on patient outcomes, methods for measuring adherence, previous studies of nonadherence in patients with cancer, common barriers to access, and interventions to improve adherence in the community setting.