Time to Initiation of Adjuvant Endocrine Therapy and Likelihood of Adherence in Medicaid-Insured Women With Breast Cancer

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In a population-based retrospective cohort study reported in JAMA Network Open, Sood et al found that longer time to adjuvant endocrine therapy initiation in Medicaid-insured women with breast cancer was associated with a reduced likelihood of short- and long-term adherence to treatment.

As stated by the investigators, “Though adjuvant endocrine therapy has proven efficacy in treating hormone receptor–positive breast cancer, patient adherence to adjuvant endocrine therapy and continuation of treatment as recommended by guidelines remain suboptimal, especially for low-income patients.”

Study Details

The study involved 1,711 women identified from the linked Missouri Cancer Registry and Medicaid claims data set. They were aged < 65 years at diagnosis of hormone receptor–positive breast cancer between January 2007 and December 2013 and followed for 5 years after the first use of adjuvant endocrine therapy through December 2018.

Time to initiation of adjuvant endocrine therapy was the number of days from date of last treatment (surgery, radiotherapy, or chemotherapy) to the first date of adjuvant endocrine therapy prescription fill. Adherence was defined as a medication possession ratio of ≥ 80%, and continuation of adjuvant endocrine therapy was defined as no gap in medication supply for at least 90 days. Odds ratios (ORs) for adherence and continuation were derived from logistic regression adjusted for demographic, clinical, and neighborhood variables.

Key Findings

Median time to initiation of adjuvant endocrine therapy was 53 days (interquartile range = 26–117 days). Among the 1,711 women, 1,317 (77.0%) were adherent during the first year after initiation, with 376 (22.0%) remaining adherent for 5 years. A total of 1,015 (59.3%) continued adjuvant endocrine therapy during the first year, with 409 (23.9%) continuing adjuvant endocrine therapy for 5 years.

Longer time to initiation was significantly associated with poorer adherence in all 5 years. Each 1-month increase in time to initiation was associated with an odds ratio of 0.97 (95% confidence interval [CI] = 0.95–0.99) for 1-year adherence and an odds ratio of 0.94 (95% CI = 0.90–0.97) for 5-year adherence.

Longer time to initiation was associated with a significantly lower likelihood of adjuvant endocrine therapy continuation during years 1 and 2, but not in years 3 to 5. Odds ratios for each 1-month increase in time to initiation were 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.

Among other factors associated with likelihood of adherence:

  • Rural vs urban patients had a significantly greater likelihood of adherence for 2 years (OR = 1.43, 95% CI = 1.12–1.82) to 5 years (OR = 1.65, 95% CI = 1.24–2.20)
  • Unmarried vs married women had significantly reduced likelihood of adherence for 1 year (OR = 0.63, 95% CI = 0.48–0.84) and for 5 years (OR = 0.73, 95% CI = 0.56–0.94).

Additional factors associated with likelihood of continuation included race, with non-Hispanic Black patients vs non-Hispanic White patients having decreased likelihood for the first year (OR = 0.75, 95% CI = 0.58–0.97) and at 5 years (OR = 0.63, 95% CI = 0.46–0.87).

The investigators concluded, “In this cohort study, longer time to adjuvant endocrine therapy initiation was associated with lower odds of short-term and long-term adherence to adjuvant endocrine therapy 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.”

Ying Liu, PhD, MD, of the Division of Public Health Sciences, Department of Surgery, Washington University School of Medicine, is the corresponding author for the JAMA Network Open article.

Disclosure: The study was supported by the National Cancer Institute, American Cancer Society, and others. For full disclosures of the study authors, visit

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