Introduction of Generic Aromatase Inhibitors Reduces Decline in Adherence in Medicare D Breast Cancer Patients Without Low-Income Subsidy


Key Points

  • Introduction of generic aromatase inhibitors did not significantly affect adherence decline among Medicare D patients with low-income subsidies.
  • Among patients without low-income subsidies, introduction of generic aromatase inhibitors reduced the rate of decline in adherence.

Adherence to aromatase inhibitor treatment for breast cancer declines over time. In a study reported in the Journal of the National Cancer Institute, Neuner et al found that introduction of generic aromatase inhibitors resulted in a reduction in decline in adherence among patients with breast cancer enrolled in Medicare D who did not receive low-income subsidies.

Study Details

The study involved data on 16,462 Medicare D enrollees with incident breast cancer in 2006 and 2007. Medicare D claims were used to calculate aromatase inhibitor adherence, defined as medication possession ratio ≥ 80% of eligible days, over 36 months. The effect of introduction of generic anastrozole (July 2010) and generic letrozole and exemestane (April 2011) on adherence was analyzed.

Effect on Adherence

Adherence declined throughout the study, with subsidy recipients having higher adherence rates than nonrecipients throughout. For women without a subsidy, the median quarterly out-of-pocket cost of anastrozole decreased from a high of $183 in the fourth quarter of 2009 to $15 in the fourth quarter of 2011 and that of the other aromatase inhibitors decreased from $81 in the first quarter of 2011 to $16 in the fourth quarter of 2011. Declines in adherence were attenuated with the generic aromatase inhibitor introductions, with adjusted adherence probabilities estimated to be 5.4% higher after introduction of generic anastrozole and 11% higher after introduction of generic letrozole/exemestane.

Among patients without a subsidy, analysis by yearly quarter after introduction of generic anastrozole showed adjusted odds ratios (ORs) for adherence ranging from 1.08 (95% [confidence interval] = 1.02–1.14) in quarter 1 to 1.51 (95% CI = 1.44–1.58) in quarter 4, a quarter that typically has the lowest adherence rates during the year after starting a treatment. Overall, the adjusted odds ratio for adherence among patients without subsidies after introduction of generic letrozole/exemestane was 1.47 (95% CI = 1.40–1.55).

The investigators concluded: “The introduction of generic medications attenuated the decline in adherence to [aromatase inhibitors] over three years of treatment among breast cancer survivors not receiving low-income subsidies for Medicare D coverage.”

Joan Neuner, MD, MPH, of Medical College of Wisconsin, is the corresponding author for the Journal of the National Cancer Institute article.

The study was supported by the American Cancer Society and National Institutes of Health.

The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.