Development and psychometric evaluation of the adjuvant endocrine therapy beliefs scale for breast cancer survivors

Purpose: Adjuvant endocrine therapy has a vital role in reducing breast cancer mortality. The beliefs in adjuvant endocrine therapy is a very important factor in the medication adherence of breast cancer survivors. Therefore, it is necessary to develop a standardized scale for assessment of adjuvant endocrine therapy. The purpose of this study was to identify the attributes of adjuvant endocrine therapy beliefs, and to evaluate adjuvant endocrine therapy beliefs scale psychometric properties. Methods: A hybrid model was applied to identify the concept of adjuvant endocrine therapy beliefs and measurement question were developed by the scale development process. Statistical analysis using validity analysis and Rasch analysis based on item response theory were performed. A total of 228 breast cancer survivors in South Korea participated in the study. Results: The finally developed adjuvant endocrine therapy beliefs scale consisted of 22 items. The items extracted by 4 factors explained 59.72% of the total variance. The model fit showed an acceptable level. The adjuvant endocrine therapy beliefs scale was excellent in convergent and discriminant validity with reliability. Conclusion: This scale is expected to be practical and useful in identifying adjuvant endocrine therapy beliefs and developing intervention strategies to promote adjuvant endocrine therapy adherence. In addition, continuous education and support should be accompanied so that breast cancer survivors can maintain positive beliefs in adjuvant endocrine therapy adherence.