Factors Associated with Endocrine Therapy Non-Adherence in Breast Cancer Survivors

For women with hormone receptor positive breast cancer, long-term endocrine therapy (ET) can greatly reduce the risk of recurrence, yet adherence is low- particularly among traditionally underserved populations.

The Carolina Breast Cancer Study oversampled Black and young women (<50 years of age). Participants answered an ET-specific medication adherence questionnaire assessing reasons for non-adherence. We used principal factor analysis to identify latent factors describing ET non-adherence. We then performed multivariable regression to determine clinical and demographic characteristics associated with each ET non-adherence factor.

1,231 women were included in analysis, 59% reported at least one barrier to ET adherence. We identified three latent factors which we defined as: habit - challenges developing medication-taking behavior; tradeoffs - high perceived side effect burden and medication safety concerns; and resource barriers - challenges related to cost or accessibility. Older age (50+) was associated with less reporting of habit (Adjusted Risk Ratio (aRR) 0.54[95% CI: 0.43-0.69] and resource barriers (aRR 0.66[0.43-0.997]), but was not associated with tradeoff barriers. Medicaid-insured women were more likely than privately-insured to report tradeoff (aRR:1.53 [1.10-2.13]) or resource barriers (aRR:4.43[2.49-6.57]). Black race was associated with increased reporting of all factors (habit: aRR 1.29[1.09-1.53]; tradeoffs: 1.32[1.09-1.60], resources: 1.65[1.18-2.30]).

Barriers to ET adherence were described by three distinct factors, and strongly associated with sociodemographic characteristics. Barriers to ET adherence appear inadequately addressed for younger, Black, and publicly-insured breast cancer survivors. These findings underscore the importance of developing multi-faceted, patient-centered interventions that address a diverse range of barriers to ET adherence.