Patterns of medication adherence in a multi-ethnic cohort of prevalent statin users diagnosed with breast, prostate, or colorectal cancer
To investigate the implications of a cancer diagnosis on medication adherence for pre-existing comorbid conditions, we explored statin adherence patterns prior to and following a new diagnosis of breast, colorectal, or prostate cancer among a multi-ethnic cohort.
We identified adults enrolled at Kaiser Permanente Northern California who were prevalent statin medication users, newly diagnosed with breast, colorectal, or prostate cancer between 2000 and 2012. Statin adherence was measured using the proportion of days covered (PDC) during the 2-year pre-cancer diagnosis and the 2-year post-cancer diagnosis. Adherence patterns were assessed using generalized estimating equations, for all cancers combined and stratified by cancer type and race/ethnicity, adjusted for demographic, clinical, and tumor characteristics.
Among 10,177 cancer patients, statin adherence decreased from pre- to post-cancer diagnosis (adjusted odds ratio (ORadj):0.91, 95% confidence interval (95% CI):0.88–0.94). Statin adherence decreased from pre- to post-cancer diagnosis among breast (ORadj:0.94, 95% CI:0.90–0.99) and colorectal (ORadj:0.79, 95% CI:0.74–0.85) cancer patients. No difference in adherence was observed among prostate cancer patients (ORadj:1.01, 95% CI:0.97–1.05). Prior to cancer diagnosis, adherence to statins was generally higher among non-Hispanic whites and multi-race patients than other groups. However, statin adherence after diagnosis decreased only among these two populations (ORadj:0.85, 95% CI:0.85–0.92 and ORadj:0.86, 95% CI:0.76–0.97), respectively.
We found substantial variation in statin medication adherence following diagnosis by cancer type and race/ethnicity among a large cohort of prevalent statin users in an integrated health care setting.
Implications for Cancer Survivors
Improving our understanding of comorbidity management and polypharmacy across diverse cancer patient populations is warranted to develop tailored interventions that improve medication adherence and reduce disparities in health outcomes.
KeywordsAdherence Race/ethnicity Breast cancer Colorectal cancer Prostate cancer Comorbidities
Parts of this study were presented at the 8th American Association for Cancer Research Conference on The Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved. The study sponsor had no role in study design; collection, analysis, or interpretation of data; writing of the report; or the decision to submit the report.
This work was supported by PHS grant from the National Cancer Institute (R01 CA098838, Habel, PI; R01AG032249, Adams, PI; Cancer Research Network: U24 CA17152, Kushi, PI).
Compliance with ethical standards
Conflict of interest
MPB has received research grants from AstraZeneca, and LAH has received research grants from Genentech, for projects outside of this work.
This study was a secondary analysis of existing dataset with no PHI and, therefore, did not meet the definition of human subject research. For this type of study, formal consent is not required.
- 1.American Cancer Society. Cancer facts & figures 2018. Atlanta, GA: American Cancer Society; 2018.Google Scholar
- 2.Edwards BK, Noone AM, Mariotto AB, Simard EP, Boscoe FP, Henley SJ, et al. Annual report to the nation on the status of cancer, 1975-2010, featuring prevalence of comorbidity and impact on survival among persons with lung, colorectal, breast, or prostate cancer. Cancer. 2014;120(9):1290–314.CrossRefGoogle Scholar
- 19.Taylor F, et al. Statins for the primary prevention of cardiovascular disease. Cochrane Database Syst Rev. 2013;(1):CD004816.Google Scholar
- 29.Oehrli MD, Quesenberry CP. Northern California cancer registry: 2015 annual report on trends, incidence, and outcomes. Oakland, CA: Kaiser Permanente; 2015.Google Scholar
- 30.Nau DP. Proportion of days covered (PDC) as the preferred method of measuring medication adherence. 02/01/2016]; Available from: www.pqaalliance.org/images/uploads/files/PQA%20PDC%20vs%20%20MPR.pdf.
- 33.Fitzmaurice GM, Laird NM, Ware JH, editors. Applied longitudinal analysis. Second ed. New York, New York: John Wiley and Sons; 2011.Google Scholar
- 36.Tam-McDevitt J. Polypharmacy, aging, and cancer. Oncology (Williston Park). 2008;22(9):1052–5 discussion 1055, 1058, 1060.Google Scholar
- 47.Darkow T, Henk HJ, Thomas SK, Feng W, Baladi JF, Goldberg GA, et al. Treatment interruptions and non-adherence with imatinib and associated healthcare costs: a retrospective analysis among managed care patients with chronic myelogenous leukaemia. Pharmacoeconomics. 2007;25(6):481–96.CrossRefGoogle Scholar