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Open Access Research article

Adherence evaluation of endocrine treatment in breast cancer: methodological aspects

Anne S Oberguggenberger1, Monika Sztankay1, Beate Beer2, Birthe Schubert2, Verena Meraner1, Herbert Oberacher2, Georg Kemmler1, Johannes Giesinger1, Eva Gamper1, Barbara Sperner-Unterweger1, Christian Marth3, Bernhard Holzner1 and Michael Hubalek3*

Author Affiliations

1 Department of Psychiatry and Psychotherapy, Innsbruck Medical University, Anichstraße 35, 6020, Innsbruck, Austria

2 Institute of Legal Medicine, Innsbruck Medical University, Anichstraße 35, 6020, Innsbruck, Austria

3 Department of Obstetrics and Gynecology, Innsbruck Medical University, Anichstraße 35, 6020, Innsbruck, Austria

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BMC Cancer 2012, 12:474  doi:10.1186/1471-2407-12-474

Published: 15 October 2012

Abstract

Background

Current studies on adherence to endocrine therapy in breast cancer patients suffer from methodological limitations due to a lack of well-validated methods for assessing adherence. There is no gold standard for measuring adherence. The aim of our study was to compare four different approaches for evaluating adherence to anastrozole therapy for breast cancer with regard to concordance between methods.

Methods

Outpatients with early breast cancer treated with anastrozole completed the multi-method assessment of adherence. We implemented a self-report scale (the Simplified Medication Adherence Questionnaire), physician- ratings, refill records and determination of anastrozole serum concentration.

Results

Comparison of the four approaches using Spearman rank correlation revealed poor concordance across all methods reflecting weak correlations of 0.2-0.4. Considering this data incomparability across methods, we still observed high adherence rates of 78%-98% across measures.

Conclusion

Our findings contribute to the growing body of knowledge on the impact that methodological aspects exert on the results of adherence measurement in breast cancer patients receiving endocrine treatment. Our findings suggest that the development and validation of instruments specific to patients receiving endocrine agents is imperative in order to arrive at a more accurate assessment and to subsequently obtain more precise estimates of adherence rates in this patient population.

Keywords:
Breast neoplasm; Endocrine therapy; Patient compliance; Method; Adherence