title: Hormonal contraceptive use and breast cancer in Thai women.
abstract: BACKGROUND
  Breast cancer is the most common cancer in women worldwide. We investigated the association of hormonal contraceptive use and breast cancer in Thai women.
  
  
  METHODS
  A cohort study was conducted in Khon Kaen, Thailand. There were 70 cases of histologically confirmed breast cancer among 11 414 women aged 30 to 69 years who were recruited as participants in the cohort study during the period from 1990 through 2001. The study population was followed-up until December 31, 2011. To identify factors associated with incidence of breast cancer, hazard ratios (HRs) and 95% confidence intervals (CIs) were estimated using a Cox proportional hazards model.
  
  
  RESULTS
  The 11 414 women provided a total observation time of 157 200 person-years. Breast cancer risk among women with a history of hormonal contraceptive use was 1.31 times that of women without such a history, but the difference was not statistically significant (95% CI, 0.65-2.65). No type of hormonal contraceptive was associated with a significant increase in breast cancer risk as compared with women who had never used hormonal contraceptives (oral contraception: HR = 1.35, 95% CI, 0.65-2.78; injection contraception: HR = 1.25, 95% CI, 0.56-2.80), and there was no relationship between duration of hormonal contraceptive use and breast cancer.
  
  
  CONCLUSIONS
  There was no association between hormonal contraceptive use and breast cancer; however, this finding should be viewed with caution due to the small number of cases.
authors.affiliation: Department of Epidemiology, Faculty of Public Health, Khon Kaen University.
authors.forename: Arisara
authors.initials: A
authors.lastname: Poosari
authors.forename: Supannee
authors.initials: S
authors.lastname: Promthet
authors.forename: Siriporn
authors.initials: S
authors.lastname: Kamsa-ard
authors.forename: Krittika
authors.initials: K
authors.lastname: Suwanrungruang
authors.forename: Jirapat
authors.initials: J
authors.lastname: Longkul
authors.forename: Surapon
authors.initials: S
authors.lastname: Wiangnon
mesh_terms: D000328:Adult; D000368:Aged; D001943:Breast Neoplasms / Q000139:chemically induced / Q000453:epidemiology*; D003271:Contraceptive Agents, Female / Q000009:adverse effects / Q000627:therapeutic use*; D003278:Contraceptives, Oral, Hormonal / Q000009:adverse effects / Q000627:therapeutic use*; D005260:Female; D006801:Humans; D007267:Injections; D008875:Middle Aged; D012307:Risk Factors; D013785:Thailand / Q000453:epidemiology
chemical_list: D003271:Contraceptive Agents, Female; D003278:Contraceptives, Oral, Hormonal