Abstract
BACKGROUND: Extending adjuvant endocrine therapy (AET) from 5 to 10 years has been shown to improve disease-free survival (DFS) in hormone receptor-positive (HR+) women with breast cancer. However, adherence to AET for 5 years remains suboptimal, with side effects frequently identified as a major contributing factor. Additionally, the impact of side effects on 5-year adherence has rarely been comprehensively explored. PURPOSE: This review aimed to consolidate studies published in English or Chinese on the side effects of AET and their impact on 5-year adherence in women with breast cancer. METHODS: This integrative review followed Whittemore and Knafl's five-stage framework. Seven electronic databases (Medline, Cochrane Library, Embase, CINAHL, PsycINFO, Scopus and China National Knowledge Infrastructure) were searched from their inception to February 2025, following strict inclusion and exclusion criteria. Methodological quality was evaluated using the Mixed Methods Appraisal Tool (version 2018). RESULTS: Thirty-four eligible articles were included, comprising 20 quantitative, 12 qualitative, and two mixed-methods studies. The 5-year AET adherence ranged from 46% to 93.6%, with a consistent decline over time. Musculoskeletal and joint pain, hot flashes, personal images, sleep issues, and emotional disturbances were the most common side effects. Although the number and severity of side effects have been identified as critical factors affecting adherence, the impact of side effects on AET adherence has been inconsistent across studies. Current studies lack standardized methods for measuring adherence and clear distinctions between the side effects of different AETs. Many women reported inadequate understanding and strategies for managing side effects, which not only diminished their quality of life (QoL) but also led to premature discontinuation. CONCLUSION: Future research should explore a comprehensive, multi-method adherence instrument and differentiate the side effects of various AETs. Targeted interventions are required to support women better and improve their long-term adherence to AET.