Importance: Randomized trials in breast cancer have demonstrated the clinical benefits of adjuvant endocrine therapy (AET) in preventing recurrence and death. The examination of concordance with AET guidelines at a national level as a measure of quality of care is important.
Objective: To investigate temporal trends and factors related to receipt of AET for breast cancer.
Design, setting, and participants: This retrospective cohort study included 981 729 women with breast cancer in the National Cancer Database from January 1, 2004, to December 31, 2013. Women with stages I to III breast cancer who received all or part of their treatment at the reporting institution were included in the analysis.
Main outcomes and measures: Temporal changes in AET receipt (estimating the annual percentage change) and AET practice patterns (using logistic regression) and the effect of AET guideline concordance on survival of women with hormone receptor-positive (HR+) breast cancer (using the multivariable Cox proportional hazards model).
Results: Of the 981 729 eligible patients (mean [SD] age, 60.8 [13.3] years), 818 435 had HR+ and 163 294 had HR-negative (HR-) cancer. Among the patients with HR+ cancer, receipt of AET increased over time, from 69.8% in 2004 to 82.4% in 2013. Among patients with HR- cancer, receipt decreased from 5.2% in 2004 to 3.4% in 2013. Hospital-level adherence (≥80% of patients with HR+ cancer received AET) increased from 40.2% in 2004 to 69.2% in 2013. Receipt of AET varied significantly by age (lower in patients ≥80 years), race (lower in African American and Hispanic participants), geographic location (lower in West South Central, Mountain, and Pacific census regions), and receptor status (lower in patients with estrogen receptor-negative and progesterone receptor-positive cancer). Surgery and radiotherapy were the factors most significantly associated with appropriate AET receipt (only 45.0% in patients who received lumpectomy without radiotherapy). Receipt of AET was associated with a 29% relative risk reduction in mortality. Based on this effectiveness estimate, if all patients with HR+ cancer received AET, approximately 14 630 lives would have been saved over 10 years.
Conclusions and relevance: From 2004 to 2013, underuse and misuse of AET have decreased for patients with breast cancer, but optimal use has not been achieved, and significant variation in care remains. The involvement of surgery and radiotherapy were among the most significant factors associated with optimal use, which underscores the benefits of team-based care to support guideline-concordant therapy.