title: Patterns and reasons for switching classes of hormonal therapy among women with early-stage breast cancer.
abstract: OBJECTIVE
  Breast cancer patients can switch hormonal therapy (HT) regimens due to treatment side effects or menopausal status change. We describe HT class switching from aromatase inhibitor (AI) to tamoxifen (TAM), and vice versa.
  
  
  METHODS
  In a cohort of 3,265 women diagnosed with hormone-receptor-positive breast cancer at Kaiser Permanente Northern California from 2005 to 2013, we analyzed prescription records, switching reasons, and treatment adherence post-switch by chart review, through 31 December 2014.
  
  
  RESULTS
  There were 290 women who switched from AI to TAM (AI switchers), including 130 (45%) switchers during the first year of treatment; and 446 women who switched from TAM to AI (TAM switchers), including 120 (27%) switchers within the first year. After the switch, 136 (47%) AI switchers and 260 (58%) TAM switchers finished or remained on the planned therapy; 69 (24%) AI switchers and 99 (22%) TAM switchers discontinued therapy. AI side effects (73%), specifically joint pain/arthralgia and bone health issues, were the most common reasons for switching from AI to TAM, whereas from TAM to AI, it was menopausal status change (42%).
  
  
  CONCLUSIONS
  Study findings highlight the need for better ways to control patient symptoms from HT to prevent discontinuation, and thus ensure best prognosis.
authors.affiliation: Division of Research, Kaiser Permanente Northern California, 2000 Broadway, Oakland, CA, 94612, USA. Marilyn.L.Kwan@kp.org.
authors.forename: Marilyn L
authors.identifier: http://orcid.org/0000-0001-8863-3950
authors.initials: ML
authors.lastname: Kwan
authors.affiliation: Division of Research, Kaiser Permanente Northern California, 2000 Broadway, Oakland, CA, 94612, USA.
authors.forename: Janise M
authors.initials: JM
authors.lastname: Roh
authors.affiliation: Division of Research, Kaiser Permanente Northern California, 2000 Broadway, Oakland, CA, 94612, USA.
authors.forename: Cecile A
authors.initials: CA
authors.lastname: Laurent
authors.affiliation: Division of Research, Kaiser Permanente Northern California, 2000 Broadway, Oakland, CA, 94612, USA.
authors.forename: Jean
authors.initials: J
authors.lastname: Lee
authors.affiliation: Department of Cancer Prevention and Control, Roswell Park Cancer Institute, Elm and Carlton Streets, Buffalo, NY, 14263, USA.
authors.forename: Li
authors.initials: L
authors.lastname: Tang
authors.affiliation: Department of Medicine and the Herbert Irving Comprehensive Cancer Center, Columbia University, New York, NY, 10032, USA.
authors.forename: Dawn
authors.initials: D
authors.lastname: Hershman
authors.affiliation: Division of Research, Kaiser Permanente Northern California, 2000 Broadway, Oakland, CA, 94612, USA.
authors.forename: Lawrence H
authors.initials: LH
authors.lastname: Kushi
authors.affiliation: Department of Cancer Prevention and Control, Roswell Park Cancer Institute, Elm and Carlton Streets, Buffalo, NY, 14263, USA.
authors.forename: Song
authors.initials: S
authors.lastname: Yao
mesh_terms: D000368:Aged; D018931:Antineoplastic Agents, Hormonal / Q000009:adverse effects / Q000627:therapeutic use*; D047072:Aromatase Inhibitors / Q000009:adverse effects / Q000627:therapeutic use*; D001943:Breast Neoplasms / Q000188:drug therapy*; D002140:California; D003657:Decision Making; D057915:Drug Substitution; D005260:Female; D006801:Humans; D008875:Middle Aged; D013629:Tamoxifen / Q000009:adverse effects / Q000627:therapeutic use*
chemical_list: D018931:Antineoplastic Agents, Hormonal; D047072:Aromatase Inhibitors; D013629:Tamoxifen
keywords: Aromatase inhibitors; Breast cancer; Cancer survivor; Cohort study; Hormonal therapy; Tamoxifen