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Factors associated with endocrine therapy adherence among post-menopausal women treated for early-stage breast cancer in Ontario, Canada

  • Epidemiology
  • Published:
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Abstract

Purpose

Adherence to adjuvant endocrine therapy among post-menopausal breast cancer patients is an important survivorship care issue. We explored factors associated with endocrine therapy adherence and survival in a large real-world population-based study.

Methods

We used health administrative databases to follow women (aged ≥ 66 years) who were diagnosed with breast cancer and started on adjuvant endocrine therapy from 2005 to 2010. Adherence was measured by medical possession ratio (MPR) and characterized as low (< 39% MPR), intermediate (40–79% MPR), or high (≥ 80% MPR) over a 5-year period. We investigated factors associated with adherence using a multinomial logistic regression model. Factors associated with all-cause mortality (5 years after starting endocrine therapy) were investigated using a multivariable Cox proportional hazards model.

Results

We identified 5692 eligible patients starting adjuvant endocrine therapy who had low, intermediate, and high adherence rates of 13% (n = 749), 13% (n = 733), and 74% (n = 4210), respectively. Lower rates of adherence were associated with increased age [low vs. high adherence: odds ratio (OR) 1.03, 95% CI 1.02–1.05 (per year); intermediate vs. high adherence: OR 1.02, 95% CI 1.01–1.04 (per year)]. High adherence was associated with previous use of adjuvant chemotherapy (low versus high adherence OR 0.42, 95% CI 0.30–0.59) and short-term follow-up with a medical oncologist within 4 months of starting endocrine therapy (low versus high adherence OR 0.83, 95% CI 0.69–0.99). Unadjusted analysis showed increased survival among patients with high endocrine therapy adherence. However, an independent association was no longer clearly detected after controlling for confounders.

Conclusion

Interventions to improve adjuvant endocrine therapy adherence are warranted. Non-adherence may be a more significant issue among elderly patients. Short-term follow-up visit by a patient’s medical oncologist after starting endocrine therapy may help to improve compliance.

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Acknowledgements

This study was supported by the ICES Western site. ICES is funded by an annual grant from the Ontario Ministry of Health and Long-Term Care (MOHLTC). Core funding for ICES Western is provided by the Academic Medical Organization of Southwestern Ontario (AMOSO), the Schulich School of Medicine and Dentistry (SSMD), Western University, and the Lawson Health Research Institute (LHRI). This research was also funded by an AMOSO opportunities Grant. Parts of this material are based on data and/or information compiled and provided by the Canadian Institute for Health Information (CIHI) and Cancer Care Ontario (CCO). The opinions, results, and conclusions reported in this paper are those of the authors and do not necessarily reflect those of the funding or data sources. We thank IMS Brogan Inc. for use of their Drug Information Database. No endorsement by ICES, MOHLTC, AMOSO, SSMD, LHRI, CIHI, or CCO is intended or should be inferred.

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Authors and Affiliations

  1. Division of Medical Oncology, London Regional Cancer Program, London Health Sciences Centre, University of Western Ontario, 800 Commissioners Road East, London, ON, N6A 4L6, Canada

    Phillip S. Blanchette, Ted Vandenberg & Jacques Raphael

  2. ICES Western, London, ON, Canada

    Phillip S. Blanchette, Melody Lam, Lucie Richard, Britney Allen & Salimah Z. Shariff

  3. Division of Medical Oncology, Sunnybrook Odette Cancer Centre, University of Toronto, Toronto, ON, Canada

    Kathleen I. Pritchard & Kelvin K. W. Chan

  4. Canadian Centre for Applied Research in Cancer Control, Toronto, ON, Canada

    Kelvin K. W. Chan

  5. Division of Radiation Oncology, Sunnybrook Odette Cancer Centre, University of Toronto, Toronto, ON, Canada

    Alexander V. Louie

  6. Division of Medical Oncology, Cancer Care Manitoba, University of Manitoba, Winnipeg, MB, Canada

    Danielle Desautels

  7. ICES, University of Toronto, Toronto, ON, Canada

    Craig C. Earle

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  1. Phillip S. Blanchette
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Corresponding author

Correspondence to Phillip S. Blanchette.

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Conflicts of interest

KIP has consulted for Pfizer, Roche, Amgen, Novartis, Eisai, Genomic Health, and Myriad Genetics Laboratories. TV has consulted for Novartis and Roche. AL has consulted for AstraZeneca and received honoraria from Varian Medical Systems Inc. JR has received honoraria from F. Hoffmann-La Roche. All other authors report no conflicts.

Research involving human participants and/or animals

This article does not contain any studies with human participants or animals performed by any of the authors. The use of data in this project was authorized under Section 45 of Ontario’s Personal Health Information Protection Act, which does not require review by a research ethics board.

Informed consent

ICES is a prescribed entity under Section 45 of Ontario’s Personal Health Information Protection Act. Section 45 authorizes ICES to collect personal health information, without consent, for the purpose of analysis or compiling statistical information with respect to the management of, evaluation or monitoring of, the allocation of resources to, or planning for all or part of the health system. This project was conducted under Section 45, and approved by ICES’ Privacy and Compliance Office.

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Blanchette, P.S., Lam, M., Richard, L. et al. Factors associated with endocrine therapy adherence among post-menopausal women treated for early-stage breast cancer in Ontario, Canada. Breast Cancer Res Treat 179, 217–227 (2020). https://doi.org/10.1007/s10549-019-05430-6

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