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Facilitators and barriers to medication adherence with adjuvant endocrine therapy in women with breast cancer: a structural equation modelling approach

  • Epidemiology
  • Published:
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Abstract

Purpose

To identify a structure to explain the relationship between socio-clinico factors, necessity-concerns beliefs, and perceived barriers to adherence with adjuvant endocrine therapy (AET) amongst women with breast cancer.

Methods

Participants were 244 patients with early-stage breast cancer recruited from two tertiary hospitals from May 2015 to December 2018 who completed questionnaires on medication adherence (Simplified Medication Adherence Questionnaire), necessity-concerns beliefs (Beliefs about Medicine Questionnaire), and barriers to adherence (Adherence Starts with Knowledge Questionnaire). Socio-clinico variables were collected via interview and medical records review. Structural equation modelling was applied to examine the relationships between these variables and possible mediating effects of necessity-concerns beliefs on adherence to AET.

Results

The median age of the study participants was 61 (range 32–80) years and the median duration on AET was 1.6 (IQR 1.2–2.6) years. Adherence was positively associated with age (β = 0.145, 95% CI: 0.011 to 0.279, p = 0.034) and negatively associated with barriers (β = − 0.381, 95% CI: − 0.511 to − 0.251, p < 0.001). There was no effect of Necessity (β = 0.006, 95% CI: − 0.145 to 0.158, p = 0.933) or Concerns (β = 0.041, 95% CI: − 0.117 to 0.199, p = 0.614) on adherence. Necessity-concerns beliefs were also not significant mediators in the relationship between socio-clinico factors and medication adherence.

Conclusions

Older age and lower barriers to adherence were associated with higher adherence scores. Necessity-concerns beliefs did not have a significant effect on adherence as majority of the patients identified forgetfulness as a reason for non-adherence.

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Data availability

The datasets generated and/or analysed during the current study are not publicly available due to patient confidentiality and institutional guidelines.

Abbreviations

AET:

Adjuvant Endocrine Therapy

AI:

Aromatase Inhibitors

ASK:

Adherence Starts with Knowledge

BMQ:

Beliefs about Medicines Questionnaire

CFI:

Confirmatory Factor Index

EFA:

Exploratory Factor Analysis

NCF:

Necessity-Concerns Framework

RMSEA:

Root Mean Square Error of Approximation

SEM:

Structural Equation Modelling

SMAQ:

Simplified Medication Adherence Questionnaire

SRMR:

Standardised Root Mean Squared Residual

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Acknowledgements

The authors would like to thank the oncologists, nursing staff, research coordinators and patients at the participating sites for their contribution. The following oncologists helped in patient recruitment: Yiqing Huang, Natalie Yan Li Ngoi, Gloria Hui Jia Chan, Anand Jeyasekharan, Hon Lyn Tan, Nesaretnam Barr Kumarakulasinghe, Joan Rou-En Choo, Samuel Guan Wei Ow, Thomas I Peng Soh, Joline Si Jing Lim, Matilda Xinwei Lee, Raghav Sundar, Chee Seng Tan, Boon Cher Goh, Tan Min Chin, Angela Shien Ling Pang, Yi Wan Lim, and Vaishnavi Muthu. We are grateful to Professor Rob Horne (University College London) for the permission to use the BMQ. We also thank GlaxoSmithKline for the permission to use the ASK-12.

Funding

This trial is supported by the Singapore Cancer Society Cancer Research Grant 2014; National University Cancer Institute, Singapore (NCIS) Centre Grant Seed Funding Program (Aug 2014 Grant Call); National University Health System Bridging Funds FY17. These funding sources had no role in the design of this study, its execution, analysis, interpretation of the data, or decision to submit results.

Author information

Authors and Affiliations

  1. Saw Swee Hock School of Public Health, National University of Singapore and National University Health System, 12 Science Drive 2, #10-03F, Singapore, 117549, Singapore

    Eng Hooi Tan & Bee Choo Tai

  2. Department of Haematology-Oncology, National University Cancer Institute, NUHS, Tower Block Level 7, 1E Kent Ridge Road, Singapore, 119228, Singapore

    Andrea Li Ann Wong, Li En Yvonne Ang, Siew Eng Lim, Wan Qin Chong, Jingshan Ho & Soo Chin Lee

  3. Department of General Surgery, Ng Teng Fong General Hospital, 1 Jurong East Street 21, Singapore, 609606, Singapore

    Chuan Chien Tan

  4. Division of Oncology Pharmacy, National University Cancer Institute, NUHS, Tower Block Level 7, 1E Kent Ridge Road, Singapore, 119228, Singapore

    Patrick Wong

  5. OncoCare Cancer Centre, 6 Napier Road, #02-17/18/19, Gleneagles Medical Centre, Singapore, 258499, Singapore

    Sing Huang Tan

  6. Yong Loo Lin School of Medicine, National University of Singapore and National University Health System, 1E Kent Ridge Road, Singapore, 119228, Singapore

    Bee Choo Tai

Authors
  1. Eng Hooi Tan
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  2. Andrea Li Ann Wong
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Contributions

AW, CCT, PW, SCL and BCT participated in the design of the study and research protocol. AW, CCT, SHT, LEYA, SEL, WQC, JH, SCL significantly contributed to patient recruitment. EHT collected the data. EHT and BCT conducted the statistical analysis. All authors were involved in the writing, editing, and approval of the final manuscript.

Corresponding author

Correspondence to Bee Choo Tai.

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Conflict of interests

SCL received speaker invitations to conferences and is on the advisory board for Novartis, Pfizer, and Astra Zeneca. SCL also received research grants from Pfizer. BCT received honoraria for speaking at symposia from Boehringer Ingelheim and royalty from Wiley-Blackwell. All other authors declare that they have no conflict of interest.

Ethical approval

The study was approved by the National Healthcare Group Domain-Specific Review Board (Reference number 2014/01316). All procedures performed were in accordance with the ethical standards of the institution.

Informed consent

Written informed consent was obtained from all individual participants included in the study.

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Appendices

Appendix A

See Table 2

Table 2 Distribution of scores of the ASK-12 scale
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Appendix B

See Table 3

Table 3 Distribution of scores of the BMQ Necessity and Concerns items and scales
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Appendix C

See Table 4

Table 4 Scoring of the SMAQ
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Tan, E.H., Wong, A.L.A., Tan, C.C. et al. Facilitators and barriers to medication adherence with adjuvant endocrine therapy in women with breast cancer: a structural equation modelling approach. Breast Cancer Res Treat 188, 779–788 (2021). https://doi.org/10.1007/s10549-021-06204-9

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