Adherence to Adjuvant Endocrine Therapy in Patients With Nonmetastatic Estrogen Receptor-Positive Breast Cancer: A...

Adjuvant endocrine therapy (ET) improves the prognosis of patients with nonmetastatic estrogen receptor-positive (ER+) breast carcinoma; however, adherence is crucial to ensure its efficacy. In Brazil, data regarding adherence to ET are limited. We aimed to evaluate the adherence to ET across Brazil and the characteristics associated with adherence.

Women with nonmetastatic ER+ invasive breast carcinoma who underwent ET for at least 6 months were enrolled. Adherence was assessed using the Morisky Medication Adherence Scale-8 (MMAS-8) and defined as an MMAS-8 score of 8. The groups were compared using the chi-square or exact chi-square tests for qualitative variables and the nonparametric Mann-Whitney test for quantitative variables.

Between June 2021 and September 2023, 726 patients were included in this analysis. The adherence to ET was 58.7%. The median age of the adherent women was higher than that of the nonadherent women (58.3 years v 54.8 years; P = .009). Factors associated with adherence were nonuse of ovarian suppression (P = .004), use of anti-human epidermal growth factor receptor 2 therapy (P = .007), high European Organisation for Research and Treatment of Cancer (EORTC) Quality of Life Questionnaire C30 scores on global health status (P = .0004), role functioning (P = .03), emotional functioning (P = .0007), cognitive functioning (P < .001), and social functioning (P = .0005), and EORTC BR23 scores on body image (P < .001) and future perspective domains (P = .0198).

More than one third of the patients evaluated were not adherent to ET. Although the study did not assess the impact of interventions to improve adherence to adjuvant ET, the 58.7% adherence rate shows that this study is of utmost importance.