Association of Endocrine Therapy Initiation Timeliness With Adherence and Continuation in Low-Income Women With Breast Cancer

Abstract

Importance: Though adjuvant endocrine therapy (AET) has proven efficacy in treating hormone receptor-positive (HR-positive) breast cancer, patient adherence to AET and continuation of treatment as recommended by guidelines remain suboptimal, especially for low-income patients.

Objective: To quantify timelines for initiating AET and assess their association with short- and long-term adherence and continuation of AET in low-income women with breast cancer.

Design, setting, and participants: This population-based retrospective cohort study included women younger than 65 years diagnosed with first primary HR-positive breast cancer between January 1, 2007, and December 31, 2013, followed up for 5 years after the first use of AET through December 2018, and identified from the linked Missouri Cancer Registry and Medicaid claims data set.

Exposures: Time to initiation (TTI) as days from the date of last treatment (surgery, radiotherapy, or chemotherapy) to the first date of AET prescription fill.

Main outcomes and measures: The main outcomes were adherence to AET as medication possession ratio of 80% or greater and continuation of AET as no gap in medication supply for at least 90 days. Odds ratios (ORs) of adherence and continuation over 1 to 5 years were estimated using logistic regression adjusted for demographic, clinical, and neighborhood variables. Analyses were performed between September 1, 2020, and May 31, 2022.

Results: Among 1711 patients, median TTI was 53 (IQR, 26-117) days. A total of 1029 patients (60.1%) were aged 50 to 64 years old, 1270 (74.2%) were non-Hispanic White, and 1133 (66.2%) were unmarried. In the first year after initiation, 1317 (77.0%) were adherent and 1015 (59.3%) continued AET. Over the full 5 years, 376 (22.0%) were adherent and 409 (23.9%) continued AET. Longer TTI was significantly associated with poorer adherence at every year, with an OR of 0.97 (95% CI, 0.95-0.99) for 1-year adherence and an OR of 0.94 (95% CI, 0.90-0.97) for 5-year adherence per 1-month increase in TTI. Longer TTI was also associated with lower odds of short-term, but not long-term, continuation (OR, 0.97 [95% CI, 0.95-0.99] for 1-year continuation and 0.98 [95% CI, 0.96-0.99] for 2-year continuation).

Conclusions and relevance: In this cohort study, longer time to AET initiation was associated with lower odds of short-term and long-term adherence to AET in Medicaid-insured patients with breast cancer. Therefore, early interventions targeting treatment initiation timelines may positively impact adherence throughout the course of treatment and, therefore, outcomes.

Figure 1.. Adherence to Endocrine Therapy Over Time in Medicaid-Insured Women With Hormone Receptor–Positive Breast Cancer

Adherence was defined using a medication possession ratio (percentage of days covered by medication supply in a specified period) of at least 80%. A, Adherence over years after endocrine therapy initiation. B, Adherence in each subsequent year by adherence status in the first year of endocrine therapy. C, Adherence in each subsequent year by adherence status in the previous year of endocrine therapy. AET indicates adjuvant endocrine therapy.

Figure 2.. Associations of Time to Endocrine Therapy With Treatment Adherence and Continuation in Patients With Breast Cancer

The odds ratio (OR) was for a month increase in time to initiation of endocrine therapy and was adjusted for age, race and ethnicity, marital status, census tract–level socioeconomic deprivation, rural residency, cancer stage, and comorbidity index.

Figure 3.. Continuation of Endocrine Therapy Over Time in Medicaid-Insured Women With Hormone Receptor–Positive Breast Cancer

Continuation was defined as having no gap in medication supply for at least 90 days in a specified time period. A, Continuation over years after endocrine therapy initiation. B, Continuation in each subsequent year by continuation status in the first year of endocrine therapy. C, Continuation in each subsequent year by adherence status in the previous year of endocrine therapy. AET indicates adjuvant endocrine therapy.