Adherence to adjuvant endocrine therapy in breast cancer: a single regional Australian centre experience

Adjuvant endocrine therapy reduces cancer recurrence and improves overall survival in hormone receptor-positive breast cancer. Maintaining long-term adherence to endocrine therapy can be challenging, and non-adherence has been associated with higher recurrence rates and reduced survival. Despite its importance, data describing adherence patterns in regional Australian populations are limited. This study aimed to assess adherence to adjuvant endocrine therapy in a regional Australian cancer center and to examine factors associated with non-adherence.

A cross-sectional survey was conducted at a regional Australian cancer center between March 2023 and July 2024. Eligible participants were women receiving adjuvant oral endocrine therapy for breast cancer. Adherence was assessed using the six-item Simplified Medication Adherence Questionnaire (SMAQ). Participants also reported treatment-related side effects.

One hundred women were included, with a median age of 62.5 years. The adherence rate as determined by the SMAQ was 65%. Participants reported an average of 2.5 treatment-related side effects, with hot flashes being the most commonly reported (59%). Both the presence and number of reported side effects were associated with lower adherence. In multivariable analyses, a higher side-effect burden remained associated with adherence after adjustment for other covariates.

This study demonstrates suboptimal adherence to adjuvant endocrine therapy in a regional Australian cohort and highlights treatment-related side effects and forgetfulness as key barriers to adherence. These findings underscore the importance of proactive side-effect management and practical adherence support strategies within regional cancer care settings.