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The introduction of generic aromatase inhibitors and treatment adherence among Medicare D enrollees. J Natl Cancer Inst 2015 Aug;107(8) PMID: 25971298 PMCID: PMC4580559

Pubmed ID





BACKGROUND: Aromatase inhibitors (AIs) substantially reduce breast cancer mortality in clinical trials, but high rates of nonadherence to these long-term oral therapies have reduced their impact outside of trials. We examined the association of generic AI availability with AI adherence among a large national breast cancer cohort.

METHODS: Using a quasi-experimental prepost design, we examined the effect of generic AI introductions (7/2010 and 4/2011) on adherence among a national cohort of women with incident breast cancer in 2006 and 2007 who were enrolled in the Medicare D pharmaceutical coverage program. Medicare D claims were used to calculate AI adherence, defined as a medication possession ratio of 80% or more of eligible days, over 36 months. Multivariable logistic regression models estimated with generalized estimating equations were applied to longitudinal adherence data to control for possible confounders, including receipt of a Medicare D low-income subsidy, and to account for repeated measures. All statistical tests were two-sided.

RESULTS: Sixteen thousand four hundred sixty-two Medicare D enrollees were eligible. Adherence declined throughout the study. However, among women without a subsidy, the median quarterly out-of-pocket cost of anastrozole fell from $183 in the fourth quarter of 2009 to $15 in 2011, and declines in adherence were attenuated with generic AI introductions. Regression-adjusted adherence probabilities were estimated to be 5.4% higher after generic anastrozole was introduced in 2010 and 11% higher after generic letrozole/exemestane was introduced in 2011. Subsidy recipients had higher adherence rates throughout the study.

CONCLUSIONS: The introduction of generic medications attenuated the decline in adherence to AIs over three years of treatment among breast cancer survivors not receiving low-income subsidies for Medicare D coverage.

Author List

Neuner JM, Kamaraju S, Charlson JA, Wozniak EM, Smith EC, Biggers A, Smallwood AJ, Laud PW, Pezzin LE


John A. Charlson MD Associate Professor in the Medicine department at Medical College of Wisconsin
Sailaja Kamaraju MD Associate Professor in the Medicine department at Medical College of Wisconsin
Purushottam W. Laud PhD Professor in the Institute for Health and Equity department at Medical College of Wisconsin
Joan Neuner MD, MPH Associate Professor in the Medicine department at Medical College of Wisconsin
Liliana Pezzin PhD, JD Professor in the Medicine department at Medical College of Wisconsin


2-s2.0-84939643031   24 Citations

MESH terms used to index this publication - Major topics in bold

Aged, 80 and over
Antineoplastic Agents
Aromatase Inhibitors
Breast Neoplasms
Cohort Studies
Drug Costs
Drugs, Generic
Evaluation Studies as Topic
Medication Adherence
Non-Randomized Controlled Trials as Topic
United States
jenkins-FCD Prod-332 f92a19b0ec5e8e1eff783fac390ec127e367c2b5