Endocrine therapy adherence: a cross-sectional study of factors affecting adherence and discontinuation of therapy

Adjuvant endocrine therapy for at least 5 years improves oncological outcomes in oestrogen receptor-positive breast cancer. Adherence rates to prescribed endocrine therapy are low and the search for modifiable causes of this continues. The aim of this study was to assess adherence rates in an Irish cohort of breast cancer patients prescribed adjuvant endocrine therapy and to assess modifiable factors associated with suboptimal adherence.

A cross-sectional anonymous survey was performed on 261 patients currently prescribed endocrine therapy. Data were collected regarding demographics, treatment, social and emotional factors and medication side effects. Each patient completed a medication adherence score and provided information about discontinuation of therapy and reasons for same.

Only 67.8 % of patients assessed demonstrated complete medication adherence on the medication adherence scale. Twenty-nine patients (10.9 %) permanently stopped taking their prescribed endocrine therapy. Suboptimal adherence was more likely in younger patients (p < 0.001), those in employment (p = 0.005), those who experienced side effects (p = 0.006), those who perceived themselves to have low levels of emotional support (p < 0.001) and those who use the internet to read about their illness (p = 0.003).

Endocrine therapy adherence is suboptimal in almost one-third of patients in our cohort. Appropriate assessment and management of side effects and negative emotions, combined with direction of patients to accurate internet sources of information, could help improve endocrine therapy adherence in women with early-stage breast cancer.