Impact of preexisting mental illness on breast cancer endocrine therapy adherence
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Patients with estrogen receptor positive (ER+) breast cancer are often non-adherent to endocrine therapies, despite clear survival benefits. We utilized a nationally representative cancer cohort to examine the role of specific mental illnesses on endocrine therapy adherence.
Using the SEER-Medicare database, we included 21,894 women aged 68+ at their first surgically treated stage I-IV ER+ breast cancer during 2007–2013. All had continuous fee-for-service Medicare Parts A and B for 36+ months before, 18+ months after diagnosis, and continuous Part D for 4+ months before, 18+ after diagnosis. Mental illness was defined as occurring in the 36 months prior to cancer onset. We analyzed endocrine therapy adherence, initiation, and discontinuation using longitudinal linear and Cox regression models.
Unipolar depression (11.0%), anxiety (9.5%), non-schizophrenia psychosis (4.6%), and dementias (4.6%) were the most prevalent diagnoses. Endocrine therapies were initiated by 80.0% of women. Among those with at least one year of use, 28.0% were non-adherent (< 0.80 adherence, mean = 0.84) and 25.7% discontinued. Patients with dementia or bipolar depression/psychotic/schizophrenia disorders had lower adjusted initiation probabilities by year one of follow-up, versus those without these diagnoses [0.74 95% CI (0.73–0.74) and 0.73 (0.72–0.73), respectively, reference 0.76 (0.76–0.77)]. Patients with substance use or anxiety disorders less frequently continued endocrine therapy for at least one year, after adjustment, [0.85 95% CI (0.85–0.86) and 0.88 (0.87–0.88), respectively, reference 0.90 (0.89–0.90)]. Patients with substance use disorders had 2.3% lower adherence rates (p < 0.001).
Nearly one-quarter of female Medicare beneficiaries have diagnosed mental illness preceding invasive breast cancer. Those with certain mental illnesses have modestly reduced rates of initiation, adherence, and discontinuation and this may help define patients at higher risk of treatment abandonment. Overall, endocrine therapy adherence remains suboptimal, unnecessarily worsening recurrence and mortality risk.
KeywordsPreexisting mental illness Endocrine therapy Adherence SEER-Medicare
This work was supported by the University of Iowa Holden Comprehensive Cancer Center Population Research Core (P30 CA086862), and the University of Iowa Medical Scientist Training Program (T32 GM007337). This study used the linked SEER-Medicare database. The interpretation and reporting of these data are the sole responsibility of the authors. The authors acknowledge the efforts of the National Cancer Institute; the Office of Research, Development, and Information, CMS; Information Management Services (IMS), Inc.; and the Surveillance, Epidemiology, and End Results (SEER) Program tumor registries in the creation of the SEER-Medicare database. The collection of cancer incidence data used in this study was supported by the California Department of Public Health as part of the statewide cancer reporting program mandated by California Health and Safety Code Section 103885; the National Cancer Institute’s Surveillance, Epidemiology, and End Results Program under contract HHSN261201000140C awarded to the Cancer Prevention Institute of California, contract HHSN261201000035C awarded to the University of Southern California, and contract HHSN261201000034C awarded to the Public Health Institute; and the Centers for Disease Control and Prevention’s National Program of Cancer Registries, under agreement # U58DP003862-01 awarded to the California Department of Public Health. The ideas and opinions expressed herein are those of the author(s) and endorsement by the State of California Department of Public Health, the National Cancer Institute, and the Centers for Disease Control and Prevention or their Contractors and Subcontractors is not intended nor should be inferred. The authors acknowledge the efforts of the National Cancer Institute; the Office of Research, Development, and Information, CMS; Information Management Services (IMS), Inc.; and the Surveillance, Epidemiology, and End Results (SEER) Program tumor registries in the creation of the SEER-Medicare database.
Compliance with ethical standards
Conflict of interest
Dr. Fiedorowicz reports a consultation role with Myriad Genetics, Inc. (consultation for mood disorder proteomics study), as well as research funding from Myriad Genetics, Inc. (not applied to this work). Mr. Haskins, and Drs. McDowell, Carnahan, Wallace, Smith, and Chrischilles have no disclosures or conflict of interest to report.
This study did not involve any direct human interventions. All research and analysis was performed in compliance with the current University of Iowa IRB regulations and laws of the United States.
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