title: Lifestyle influences on the association between pre-diagnostic hormone replacement therapy and breast cancer prognosis - results from The Danish 'Diet, Cancer and Health' prospective cohort.
abstract: OBJECTIVE
  The association between pre-diagnostic hormone replacement therapy (HRT) and breast cancer specific mortality as well as potential influences from other lifestyle factors on the association was investigated.
  
  
  METHODS
  Female participants from the prospective cohort "Diet, Cancer, and Health" diagnosed with breast cancer (BC) were identified and their pre-diagnostic HRT use evaluated for association with tumour biology and breast cancer outcome in multivariate analysis.
  
  
  METHODS
  Breast cancer specific mortality.
  
  
  RESULTS
  Of the 1212 patients originally considered 1064 were included. Of these, 105 women died from breast cancer during a median follow-up of 6.3 years (range 0.2-14.3 years). In multivariate analyses women who used HRT at enrolment into the cohort study had 47% lower risk of dying from breast cancer as compared to women who had previously or never used HRT (adjusted HR: 0.53; 95% CI, 0.37-0.85). Pre-diagnostic HRT use was associated with smaller tumour size at the time of diagnosis and a higher frequency of receptor positive breast cancer. Paradoxically, a high pre-diagnostic intake of vitamin D supplements was associated with HRT use but also with a higher BC specific mortality (HR: 1.47; 95% CI, 1.07-2.00) CONCLUSIONS: HRT use at enrolment was associated with breast tumours of smaller size at the time of diagnosis and positive receptor status, and with a lower BC mortality. The found association between vitamin D from supplements and higher BC mortality warrants further exploration.
authors.affiliation: Unit of Diet, Genes, and Environment, Danish Cancer Society Research Center, Denmark. Electronic address: marhol@cancer.dk.
authors.forename: Marianne
authors.initials: M
authors.lastname: Holm
authors.affiliation: Unit of Diet, Genes, and Environment, Danish Cancer Society Research Center, Denmark.
authors.forename: Anja
authors.initials: A
authors.lastname: Olsen
authors.affiliation: Department of Breast Surgery and Danish Breast Cancer Cooperative Group, Rigshospitalet, University of Copenhagen, Denmark.
authors.forename: Niels
authors.initials: N
authors.lastname: Kroman
authors.affiliation: Unit of Diet, Genes, and Environment, Danish Cancer Society Research Center, Denmark.
authors.forename: Anne
authors.initials: A
authors.lastname: Tjønneland
mesh_terms: D001943:Breast Neoplasms / Q000453:epidemiology* / Q000401:mortality / Q000517:prevention & control; D015331:Cohort Studies; D003718:Denmark / Q000453:epidemiology; D004032:Diet; D005260:Female; D020249:Hormone Replacement Therapy; D006801:Humans; D008019:Life Style; D008875:Middle Aged; D015999:Multivariate Analysis; D017698:Postmenopause; D011446:Prospective Studies; D016019:Survival Analysis; D016387:Women's Health
keywords: Breast cancer prognosis; Hormone replacement therapy; Lifestyle; Mortality; Tumour profile; Vitamin D supplement