title: Impact of hormone replacement therapy use on mammographic screening outcomes.
abstract: OBJECTIVE
  This study aims to measure the impact of HRT use at the time of screening on rates of screen-detected invasive breast cancer (IBC) and ductal carcinoma in situ (DCIS), interval cancers and investigative procedures, within a well-established population-based mammography screening program.
  
  
  METHODS
  Using South Australian BreastScreen data from 1998 to 2009 pertaining to 819,722 screening episodes, Poisson regression models were undertaken to estimate the incidence risk ratios (IRR) for various screening outcomes at both the first and subsequent screening rounds, among women who had been using HRT in the 6 months prior to screening compared with those who had not.
  
  
  RESULTS
  Current HRT use was associated with increased risk of recall for assessment, biopsy procedures, and breast cancer diagnosis among BreastScreen participants. Risk of screen-detected breast cancer was increased at subsequent screening rounds (IRR = 1.30, 95% confidence interval 1.18-1.34), but not at women's first screening round (1.05, 0.88-1.25). This increased risk applied to IBC (1.35, 1.27-1.45), but not to DCIS (1.04, 0.89-1.23). Interval cancer risk was elevated among HRT users following both the first screen (1.77, 1.33-2.37) and subsequent screening episodes (1.92, 1.72-2.15).
  
  
  CONCLUSIONS
  Increased risks of recall, biopsy rates, screen-detected, and interval cancers among HRT users have important implications for population-based breast cancer screening programs. Our findings support the concept that HRT use may increase the growth of preexisting cancers. Lack of effect on DCIS could imply different etiology or time frames for DCIS and IBC development or increased transition from preinvasive to invasive disease due to HRT use.
authors: School of Population Health, University of Adelaide, Adelaide, SA, Australia. kerri.beckmann@adelaide.edu.au
authors: Kerri R
authors: KR
authors: Beckmann
authors: Gelareh
authors: G
authors: Farshid
authors: David M
authors: DM
authors: Roder
authors: Janet E
authors: JE
authors: Hiller
authors: John W
authors: JW
authors: Lynch
mesh_terms: D000328:Adult; D000368:Aged; D001943:Breast Neoplasms / Q000139:chemically induced / Q000000981:diagnostic imaging / Q000453:epidemiology*; D002285:Carcinoma, Intraductal, Noninfiltrating / Q000139:chemically induced / Q000000981:diagnostic imaging / Q000453:epidemiology; D005260:Female; D020249:Hormone Replacement Therapy / Q000009:adverse effects*; D006801:Humans; D008327:Mammography; D008875:Middle Aged; D009361:Neoplasm Invasiveness