Endocrine therapy use in the twenty-first century: usage rates and temporal trends illustrate opportunities for improvement for South Carolina Medicaid women.

Purpose: This study examines endocrine therapy (ET) non-initiation, non-adherence, and duration by age, race, temporal trend for South Carolina Medicaid-enrolled women diagnosed with estrogen receptor-positive breast cancer between 2000 and 2014 (N = 3830).

Methods: Age, race, relative risk, and median duration of ET use were compared. Temporal trends in ET non-initiation, non-adherence, and duration were observed using linear and logistic regression models, controlling for age and race.

Results: Fifty-three percent of women in the sample did not initiate ET, with highest non-initiation rates among African Americans and survivors under age 50. Of those who did initiate ET, 42% were non-adherent with a median ET usage duration of 37 months. Twenty-one percent of initiators continued taking ET for 5 years or more. There was no change in the odds of ET non-initiation from 2000 to 2004 (OR 1.02, p = 0.67). The odds of ET non-initiation decreased from 2005 to 2009 (OR 0.81, p < 0.001) but then increased from 2010 to 2014 (OR 1.08, p = 0.002). There was no change in the odds of ET non-adherence from 2000 to 2006 (OR 1.02, p = 0.53), but from 2007 to 2012, the odds of ET non-adherence decreased each year (OR 0.93, p = 0.02). The average ET usage duration was increasing from 2000 to 2006 (β = 2.74, p < 0.001) but decreasing from 2006 to 2012 (β = - 1.46, p < 0.001).

Conclusions: This study provides a realistic picture of the challenges associated with ET usage among South Carolina Medicaid breast cancer patients. It particularly highlights small improvements over time in ET usage rates, indicating more opportunities for improvement in ET initiation, adherence, and duration among younger women of lower socio-economic status.