Cheaper Generic AIs Boost Treatment Adherence

Fran Lowry

August 27, 2015

The introduction of generic versions of aromatase inhibitors (AIs), which are substantially cheaper than the branded products, has improved adherence in breast cancer survivors not receiving low-income subsidies for Medicare D coverage.

Adherence improved by 5% to 11% after generics became available, report Joan M. Neuner, MD, MPH, and colleagues from the Medical College of Wisconsin in Milwaukee, in a study published in the August issue of the Journal of the National Cancer Institute.

And patients who received low-income subsidies had higher adherence rates throughout the study period.

"This novel finding supports the effectiveness of the Medicare D subsidy policy in improving disparities in endocrine therapy use by socioeconomic status," the authors write. "Socioeconomic disparities have been found throughout the continuum of breast cancer care, including in AI adherence. Their reversal in our study population provides evidence of a success of the LIS [low-income subsidy] program."

Poor Adherence Outside of Clinical Trials

AIs have been shown to substantially reduce breast cancer mortality in clinical trials, but nonadherence to these therapies, especially over the long term, have reduced their impact outside of such trials, the authors report.

Outside of clinical trials, one-third to one-half of patients prescribed adjuvant endocrine therapy have poor adherence or stop taking their medication completely, the authors note. Much of the nonadherence has been blamed on the adverse effects of therapy, but the expense of these medications is also a factor.

In their study, Dr Neuner and her group sought to determine whether the advent of generic, and therefore cheaper, versions of AIs made them more affordable to more women and, as a result, boosted adherence.

They used nationwide Medicare files to identify 16,462 women 65 years and older who had undergone surgery for incident breast cancer in 2006 or 2007.

All women had been continuously enrolled in fee-for-service Medicare for at least 1 year prior to surgery and had been enrolled in a standalone Medicare D prescription drug plan from the time of surgery until the first month of 2009.

Of the cohort, 5568 (33.8%) women received a low-income subsidy.

The Medicare D claims were used to calculate adherence to AIs, which was defined as a medication possession ratio of 80% of eligible days, or more, over 36 months.

Most of the women (65%) received anastrozole, and the remaining (35%) women received letrozole or exemestane.

Generic versions of anastrozole were launched in July 2010; they were followed, in April 2011, by the launch of generic versions of exemestane and letrozole.

For women without a low-income subsidy, the median quarterly out-of-pocket cost of anastrozole fell from $183 in the fourth quarter of 2009 to $15 in 2011.

After the introduction of the generic anastrozole, adherence among these women rose "considerably" — from 5.4% to 11.0%, the authors report.

For women without subsidies, 46.28% were adherent before the advent of generics, 52.79% were adherent after generic anastrozole became available, and 57.01% were adherent after generic letrozole and exemestane became available.

After generic anastrozole became available, the odds ratio for adherence was 1.51 (95% confidence interval [CI], 1.44 - 1.58); after generic letrozole and exemestane became available, the odds ratio was 1.47 (95% CI, 1.40 - 1.55).

Study Limitations

The authors acknowledge that their study has several limitations.

"Like many prior studies using pharmacy data, we were unable to examine patients who never started their medications and it is possible that there is substantial 'primary nonadherence' that we could not identify," they note.

Also, information about the extent of disease was unavailable; as a result, the study included patients of all stages. However, they note, it is "unlikely" that cancer stage explains the differences in adherence that were found in the study.

Another limitation is the use of prescription fills as a proxy for adherence.

Dr Neuner and her team conclude by calling for the federal government to improve patient supports, such as low-income subsidies, in the future.

"Attention to such strategies is important; alternative behavioral interventions to improve adherence have been costly, complicated, and labor intensive, and have had small effects at best. Regulatory efforts to enhance rapid and continuing competition by generics, promote legislative coverage of drugs that reduce mortality, or directly reduce out-of-pocket costs would likely improve patient medication adherence," they write.

This work was funded by the American Cancer Society and by the National Institutes of Health. Dr Neuner and her coauthors have disclosed no relevant financial relationships.

J Natl Cancer Inst. 2015;107:djv130. Abstract

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