title: Factors modifying the association between hormone-replacement therapy and breast cancer risk.
abstract: OBJECTIVE
  Hormone-replacement therapy (HRT) is an established risk factor for breast cancer. HRT users are different from non-users with respect to socio-economic and other characteristics. There may be women where the HRT-related risk could be modulated by other factors.
  
  
  METHODS
  We conducted a population-based case-control study with 688 breast cancer cases and 724 controls to characterize HRT users and to estimate odds ratios (OR) and 95% confidence intervals (CI) for HRT use and potentially risk modifying factors.
  
  
  RESULTS
  In women aged 50 years and older, 58% of controls and 61% of cases ever used HRT. Among women in natural menopause, HRT use for 10 years and more years was associated with an increased breast cancer risk (OR 1.79, 95% CI, 1.12-2.87), but not among women in surgical menopause (OR 0.61, 95% CI, 0.09-4.17). In the subgroup of women with a positive family history of breast cancer, each year of HRT use increased the risk by 1.22 (95% CI, 1.02-1.47). Another subgroup comprised women with at least 10 diagnostic mammograms (OR 4.04, 95% CI, 1.10-14.81 for using HRT 10 or more years).
  
  
  CONCLUSIONS
  Long-term HRT use was associated with a breast cancer risk in women with natural menopause. Our findings suggest that this risk may be increased in women with a positive family history of breast cancer and in women who received frequent diagnostic mammographic screens.
authors.affiliation: Berufsgenossenschaftliches Forschungsinstitut für Arbeitsmedizin (BGFA), Institut der Ruhr-Universität Bochum, Bürkle-de-la-Camp-Platz 1, 44789, Bochum, Gemany.
authors.forename: Beate
authors.initials: B
authors.lastname: Pesch
authors.forename: Yon
authors.initials: Y
authors.lastname: Ko
authors.forename: Hiltrud
authors.initials: H
authors.lastname: Brauch
authors.forename: Ute
authors.initials: U
authors.lastname: Hamann
authors.forename: Volker
authors.initials: V
authors.lastname: Harth
authors.forename: Sylvia
authors.initials: S
authors.lastname: Rabstein
authors.forename: Christiane
authors.initials: C
authors.lastname: Pierl
authors.forename: Hans-Peter
authors.initials: HP
authors.lastname: Fischer
authors.forename: Christian
authors.initials: C
authors.lastname: Baisch
authors.forename: Christina
authors.initials: C
authors.lastname: Justenhoven
authors.forename: Ulrich
authors.initials: U
authors.lastname: Ranft
authors.forename: Thomas
authors.initials: T
authors.lastname: Brüning
mesh_terms: D000368:Aged; D001943:Breast Neoplasms / Q000139:chemically induced* / Q000453:epidemiology*; D016022:Case-Control Studies; D015914:Estrogen Replacement Therapy / Q000009:adverse effects*; D005260:Female; D005858:Germany / Q000453:epidemiology; D006801:Humans; D008875:Middle Aged; D012307:Risk Factors