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Real-World Adherence to Endocrine Therapy Plus Ovarian Suppression for Early Breast Cancer

April 20, 2021

A recent observational cohort study evaluating adherence to endocrine therapy including ovarian suppression may reassure oncologists that use of OS does not endanger ET adherence (Cancer. 2021. doi: 10.1002/cncr.33367).

Recent clinical trial successes of adding ovarian suppression to oral endocrine therapy for premenopausal women with breast cancer led Katherine E. Reeder-Hayes, MD, MBA, MS, Division of Oncology, School of Medicine, University of North Carolina at Chapel Hill, North Carolina, and colleagues to evaluate the adoption of ovarian suppression among real-world populations and the impact of ovarian suppression on endocrine therapy adherence.

This observational cohort study examined women under the age of 50 years with incident early breast cancer from 2001 to 2016. New endocrine therapy users with or without ovarian suppression were identified through the IBM MarketScan Commercial insurance claims database, which was also used to track discontinuation of or adherence to endocrine therapy. 

Within 12 months of their diagnosis after a washout period of 12 months with no prior claims, 21,948 women filled one or more prescriptions for endocrine therapy.

Dr Reeder-Hayes and colleagues found that use of ovarian suppression steadily increased to 11.3% by 2016. Of the endocrine therapy plus ovarian suppression users, 40.2% discontinued endocrine therapy early vs 48.8% of tamoxifen-alone users.

The likelihood of discontinuing endocrine therapy was similar between endocrine therapy plus ovarian suprresion users and tamoxifen-alone users (hazard ratio, 0.92; 95% confidence interval, 0.83‐1.03). Over the first year of use, approximately 30% of patients had low adherence, while the likelihood of high adherence was similar.  

“The use of [ovarian suppression] among young, commercially insured patients with breast cancer increased over time in agreement with recent clinical trial results but remained relatively low,” concluded Dr Reeder-Hayes and colleagues, adding “Nonadherence to [endocrine therapy] was common, but the use of [ovarian suppression] was not associated with lower adherence to [endocrine therapy] in this observational, nonrandomized cohort.”—Marta Rybczynski

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