title: Types of oral contraceptives and breast cancer survival among women enrolled in Medicaid: A competing-risk model.
abstract: BACKGROUND
  Oral contraceptive pills have been implicated in the pathophysiology of breast cancer. Although many studies have examined the relationship between combined oral contraceptives (COCs) and breast cancer, there is a paucity of literature that discusses progestin-only oral contraceptives (POCs) and breast cancer. The purpose of this investigation is to examine potential associations between different types of oral contraceptives and breast cancer mortality in the South Carolina Medicaid population among different racial/ethnic groups.
  
  
  METHODS
  Subjects included 4816 women diagnosed with breast cancer between 2000 and 2013. Kaplan-Meier curves were calculated to determine time-to-mortality rates among users of oral contraceptives. Competing-risks models and Cox multivariate survival models were used to estimate the hazard ratios (HRs) and 95% confidence intervals (CIs) of breast cancer and other-cause mortality, as well as all-cause mortality.
  
  
  RESULTS
  POCs were associated with a significantly decreased risk of breast cancer mortality (HR: 0.07; 95% CI: 0.01, 0.52) and a non-significant increased risk of all-cause mortality (HR: 1.04; 95% CI: 0.52, 2.07). COCs increased the risk of breast cancer mortality (HR: 1.61; 95% CI: 1.14, 2.28) and all-cause mortality (HR: 1.83; 95% CI: 1.30, 2.57).
  
  
  CONCLUSIONS
  Use of POCs may be associated with a decreased risk of breast cancer mortality. Due to the small sample size of POC users in the current study, additional research is needed to confirm these findings.
authors.affiliation: Cancer Prevention and Control Program, University of South Carolina, United States; Epidemiology & Biostatistics, Arnold School of Public Health, University of South Carolina, United States. Electronic address: msamson@email.sc.edu.
authors.forename: Marsha E
authors.initials: ME
authors.lastname: Samson
authors.affiliation: Cancer Prevention and Control Program, University of South Carolina, United States; Epidemiology & Biostatistics, Arnold School of Public Health, University of South Carolina, United States; College of Nursing, University of South Carolina, United States.
authors.forename: Swann Arp
authors.initials: SA
authors.lastname: Adams
authors.affiliation: Epidemiology & Biostatistics, Arnold School of Public Health, University of South Carolina, United States.
authors.forename: Caroline M
authors.initials: CM
authors.lastname: Mulatya
authors.affiliation: Epidemiology & Biostatistics, Arnold School of Public Health, University of South Carolina, United States.
authors.forename: Jiajia
authors.initials: J
authors.lastname: Zhang
authors.affiliation: College of Pharmacy, University of South Carolina, United States.
authors.forename: Charles L
authors.initials: CL
authors.lastname: Bennett
authors.affiliation: Cancer Prevention and Control Program, University of South Carolina, United States; Epidemiology & Biostatistics, Arnold School of Public Health, University of South Carolina, United States.
authors.forename: James
authors.initials: J
authors.lastname: Hebert
authors.affiliation: Cancer Prevention and Control Program, University of South Carolina, United States; Epidemiology & Biostatistics, Arnold School of Public Health, University of South Carolina, United States.
authors.forename: Susan E
authors.initials: SE
authors.lastname: Steck
mesh_terms: D000328:Adult; D001943:Breast Neoplasms / Q000139:chemically induced / Q000401:mortality*; D003276:Contraceptives, Oral / Q000009:adverse effects* / Q000627:therapeutic use; D005260:Female; D006801:Humans; D008484:Medicaid; D008875:Middle Aged; D012306:Risk; D015996:Survival Rate; D014481:United States
chemical_list: D003276:Contraceptives, Oral
keywords: Breast cancer; Competing risk; Health disparities; Oral contraceptives; Progestin; Survival analysis