title: Low adherence to upfront and extended adjuvant letrozole therapy among early breast cancer patients in a clinical practice setting.
abstract: OBJECTIVE
  The aim of this study was to investigate the prevalence and causes of early discontinuation and non-adherence to upfront and extended adjuvant letrozole therapy in breast cancer patients.
  
  
  METHODS
  Adherence was assessed using medical charts and longitudinal pharmacy records of 609 patients who initiated adjuvant letrozole between January 2002 and April 2011. A Cox proportional hazards regression model was adopted to identify potential predictors of non-adherence.
  
  
  RESULTS
  The overall adherence rate after 1 year of therapy was 79.5%, with cumulative rates declining to 63.7% after 3 years and 57.1% after 5 years. A significantly lower rate of adherence in the extended adjuvant group was observed compared with the upfront adjuvant group (49.0 vs. 72.5%, p < 0.001). Adverse events (50.4%) were the major cause of early discontinuation, with musculoskeletal pain (73.2%) being the single most cited reason. Additional factors correlating with non-adherence in the upfront adjuvant group included a delay in initiation of adjuvant hormone therapy, breast-conserving surgery, calcium supplements, bisphosphonate therapy and concomitant medication for co-morbidity.
  
  
  CONCLUSIONS
  We observed that approximately 57% of patients fully adhered to letrozole therapy over a 5-year treatment period, and that the adherence to extended letrozole was meaningfully lower than the upfront adjuvant letrozole in a clinical practice setting.
authors.affiliation: Division of Life and Pharmaceutical Sciences, College of Pharmacy, Ewha Womans University, Seoul, South Korea.
authors.forename: Hye-Suk
authors.initials: HS
authors.lastname: Lee
authors.forename: Ju-Yeun
authors.initials: JY
authors.lastname: Lee
authors.forename: Young-Mi
authors.initials: YM
authors.lastname: Ah
authors.forename: Hyang-Sook
authors.initials: HS
authors.lastname: Kim
authors.forename: Seock-Ah
authors.initials: SA
authors.lastname: Im
authors.forename: Dong-Young
authors.initials: DY
authors.lastname: Noh
authors.forename: Byung Koo
authors.initials: BK
authors.lastname: Lee
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D018931:Antineoplastic Agents, Hormonal / Q000008:administration & dosage*; D001943:Breast Neoplasms / Q000188:drug therapy*; D017024:Chemotherapy, Adjuvant; D005260:Female; D006801:Humans; D000077289:Letrozole; D008875:Middle Aged; D009570:Nitriles / Q000008:administration & dosage*; D010349:Patient Compliance / Q000706:statistics & numerical data; D016016:Proportional Hazards Models; D016312:Treatment Refusal; D014230:Triazoles / Q000008:administration & dosage*
chemical_list: D018931:Antineoplastic Agents, Hormonal; D009570:Nitriles; D014230:Triazoles; D000077289:Letrozole