title: Postmenopausal hormone therapy and breast cancer: a systematic review  and meta-analysis.
abstract: OBJECTIVE
  There is a rapidly evolving debate on the indications and appropriate duration of therapy for postmenopausal hormone therapy. The objective of this meta-analysis was to examine the specific relationships of postmenopausal estrogen therapy (ET), postmenopausal combined (estrogen-progestogen) hormone therapy (CHT), and the incidence of breast cancer.
  
  
  METHODS
  We performed computerized searches of MEDLINE and CancerLit through September 2003 and reviewed reference lists of retrieved studies and meta-analyses. We included English-language studies that identified noncontraceptive postmenopausal hormone use; reported on the risks of "current use" of ET and/or CHT and breast cancer incidence; were case-control, cohort, or experimental; and reported either an odds ratio (OR), relative risk (RR), or HR with CIs. Two investigators were involved during all stages of study selection and independently extracted all data selected for inclusion in meta-analyses.
  
  
  RESULTS
  Meta-analysis of 13 studies of ET and breast cancer (700,000 women) resulted in an OR of 1.16 (95% confidence limits [CL] 1.06, 1.28), with estimates for less than 5 years use 1.16 (1.02, 1.32) and more than 5 years use 1.20 (1.06, 1.37). Meta-analysis of eight studies of CHT and breast cancer (650,000 women) resulted in an OR of 1.39 (95% CL 1.12, 1.72), with estimates for less than 5 years use 1.35 (1.16, 1.57) and more than 5 years use 1.63 (1.22, 2.18).
  
  
  CONCLUSIONS
  Data from observational studies support the association of increased but considerably different risks for breast cancer incidence among current users of ET and CHT. These represent the first pooled estimates for ET. CHT estimates correspond to those from randomized trials.
authors.affiliation: Division of General Internal Medicine, Department of Medicine, New York University School of Medicine, New York, NY, USA. nirav.shah@med.nyu.edu
authors.forename: Nirav R
authors.initials: NR
authors.lastname: Shah
authors.forename: Jeff
authors.initials: J
authors.lastname: Borenstein
authors.forename: Robert W
authors.initials: RW
authors.lastname: Dubois
mesh_terms: D001943:Breast Neoplasms / Q000139:chemically induced* / Q000453:epidemiology; D015914:Estrogen Replacement Therapy / Q000009:adverse effects*; D005260:Female; D006801:Humans; D015994:Incidence; D017698:Postmenopause; D011372:Progestins / Q000009:adverse effects*; D016032:Randomized Controlled Trials as Topic; D012307:Risk Factors
chemical_list: D011372:Progestins