title: The association between trajectories of endocrine therapy adherence and mortality among women with breast cancer.
abstract: Studies examining adherence to endocrine therapy (ET) and breast cancer-related outcomes have traditionally used the proportion of days covered (PDC) by medication to define adherence which may mask true treatment-outcome associations for patients with different medication use behaviors. We use group-based trajectory models to examine the association between ET adherence patterns and mortality compared to a standard PDC adherence measure.
  
  
  
  Using Surveillance, Epidemiology and End Results-Medicare data we included 9492 women with breast cancer who initiated ET between 2007 and 2010. We excluded women who died/recurred in the 12 months after ET initiation. We used monthly group-based trajectory models to characterize longitudinal adherence patterns and adjusted Cox proportional hazard models to estimate the association between ET adherence and mortality, comparing trajectory-based adherence to traditional PDC-based measures.
  
  
  
  Trajectory models identified five adherence groups: (i) high (56.2%); (ii) quick decline (9.5%); (iii) moderate decline (7.9%); (iv) quick decline, then increase (16.0%); and (v) slow decline (10.5%). Mortality was significantly associated with group assignment; compared to the high adherers, there was a significantly higher risk of death among quick declines (HR = 1.41, 95%CI = 1.09-1.72) and moderate declines (HR = 1.25, 95%CI = 1.00-1.55). Using the standard PDC adherence measure women with adherence <80% over the year had a higher risk of death than those with adherence ≥80% (HR = 1.21, 95%CI = 1.06-1.38).
  
  
  
  Defining ET adherence using trajectory models improved adherence measurement. These models could inform clinical practice by helping to identify common adherence patterns, potential areas for intervention and better isolate adherence-related outcomes in comparative effectiveness studies. Copyright © 2016 John Wiley & Sons, Ltd.
authors.affiliation: Gillings School of Global Public Health, Department of Health Policy and Management, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.
authors.forename: Aaron N
authors.initials: AN
authors.lastname: Winn
authors.affiliation: Gillings School of Global Public Health, Department of Health Policy and Management, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.|UNC Eshelman School of Pharmacy, Division of Pharmaceutical Outcomes and Policy, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.|UNC Lineberger Comprehensive Cancer Center, Chapel Hill, NC, USA.|Cecil G. Sheps Center for Health Services Research, Chapel Hill, NC, USA.
authors.forename: Stacie B
authors.initials: SB
authors.lastname: Dusetzina
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D018931:Antineoplastic Agents, Hormonal / Q000008:administration & dosage*; D001943:Breast Neoplasms / Q000188:drug therapy* / Q000401:mortality / Q000473:pathology; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D055118:Medication Adherence; D015233:Models, Statistical; D016016:Proportional Hazards Models; D018426:SEER Program; D013997:Time Factors; D016896:Treatment Outcome
chemical_list: D018931:Antineoplastic Agents, Hormonal
keywords: adherence; breast cancer; comparative effectiveness; epidemiologic methods; outcome research; pharmacoepidemiology; trajectories