Introduction of Generic Aromatase Inhibitors Reduces Adherence to Breast Cancer Therapy

A study published in Cancer found that the introduction of generic aromatase inhibitors reduced the decrease trend of adherence to hormonal therapy for patients with breast cancer.

The decreasing trend of adherence to hormonal therapy among patients with breast cancer lessened over the course of treatment with the introduction of generic aromatase inhibitors, according to a study published in Cancer.

Even though successfully implementing the Medicare low-income subsidy (LIS) program helped minimize out-of-pocket costs for financially vulnerable patients, the researchers suggest caution for policymakers not to introduce disparities for financially vulnerable patients who do not qualify for such a program.

“The results of the current study contribute to the evidence suggesting that introducing generics into the market could improve long-term oral medication adherence among Medicare beneficiaries without the Medicare LIS, and potentially close the gap between LIS and non-LIS beneficiaries,” wrote the researchers.

The study’s population included 10,905 women, of which 62.8% of women included initiated adjuvant hormone therapy within the first year of their diagnosis. For LIS beneficiaries, the adjusted adherence was 11.4% higher than that of non-LIS beneficiaries (P < .001).

More, the group of non-LIS beneficiaries saw an overall decreasing trend of adherence (−0.035; P < .001) prior to when generic aromatase inhibitors were introduced. The same group experienced a 3.4% increase in slope 6 months after anastrozole was introduced to the market as the first generic aromatase inhibitor, with an additional 0.8% increase in slope 6 months after letrozole and exemestane were introduced (P < .001).

The researchers utilized the Surveillance, Epidemiology, and End Results (SEER)-Medicare-linked database to identify women aged 65 or older diagnosed with hormone receptor-positive breast cancer from 2007 to mid-2009.

“Policies that support additional coverage for effective oral cancer medications also may improve long-term treatment adherence,” wrote the researchers. “However, when implementing copay reduction programs, policymakers should be cautious with regard to introducing disparities among patients who are nearly poor but are ineligible for such programs.”

The goal of the study was to examine the impact of introducing generic aromatase inhibitors on adjuvant hormone therapy adherence over the entire course of treatment.

The researchers acknowledge limitations to their data, including the uncontrolled confounders due to limited available data. Specifically, this includes the inability to account for patient preferences, their knowledge of the disease, or their attitude toward treatment.

More, the results do not take into consideration patients who filled prescriptions through inpatient facilities or through supplementary insurance. As a result, the researchers suggest they may have underestimated the adherence rate for patients who received medications through non-Medicare sources.

“The findings of the current study demonstrated that, with the availability of cheaper generic medications, the decrease in adherence among patients with breast cancer attenuated over the course of their treatment,” wrote the researchers. “Regulatory efforts should be focused on enhancing the availability and promotion of the competitive markets for generic cancer medications.”


Ma S, Shepard DS, Ritter GA, et al. The Impact of the Introduction of Generic Aromatase Inhibitors on Adherence to Hormonal Therapy Over the Full Course of 5-Year Treatment for Breast Cancer. Cancer. DOI: 10.1002/cncr.32976.