title: Hormone replacement therapy, reproductive history, and colorectal adenomas: data from the Prostate, Lung, Colorectal and Ovarian (PLCO) Cancer Screening Trial (United States).
abstract: OBJECTIVE
  Findings from some epidemiologic studies of colorectal cancer and adenoma suggest that the protective effect of post-menopausal hormone replacement therapy (HRT) may differ across categories of age and body mass index (BMI). We conducted an analysis of women participating in the Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial to investigate the relationship between HRT use and prevalent adenoma, both overall and across different population subgroups.
  
  
  METHODS
  Women aged 55-74 were randomized to screening by flexible sigmoidoscopy at ten PLCO screening centers between September 1993 and September 2001. We identified 1468 women with at least one left-sided adenoma and 19,203 without adenoma or colorectal cancer. Information about HRT and reproductive factors was obtained from a self-administered questionnaire.
  
  
  RESULTS
  Compared to never use of HRT, current use was associated with a decreased prevalence of left-sided adenoma (odds ratio (OR) 0.85; 95% confidence interval (CI) 0.75-0.97). We found no evidence of dose-response with increasing duration of use for current or former users. The association with current HRT use was stronger among women aged 65+ (OR 0.69; 95% CI 0.56-0.84), with a BMI<30 (OR 0.82; 95% CI 0.71-0.95) and who regularly use aspirin or ibuprofen (OR 0.77; 95% CI 0.65-0.91). Other reproductive factors were not significantly associated with adenoma prevalence.
  
  
  CONCLUSIONS
  Our findings suggest that current HRT use may protect against colorectal adenoma, and that this protective effect is short-lived following cessation of use.
authors.affiliation: Occupational and Environmental Epidemiology Branch, Division of Cancer Epidemiology and Genetics, National Cancer Institute, 6120 Executive Blvd., MSC 7240, Executive Plaza South/8121, Rockville, MD 20892, USA. purduem@mail.nih.gov
authors.forename: Mark P
authors.initials: MP
authors.lastname: Purdue
authors.forename: Pamela J
authors.initials: PJ
authors.lastname: Mink
authors.forename: Patricia
authors.initials: P
authors.lastname: Hartge
authors.forename: Wen-Yi
authors.initials: WY
authors.lastname: Huang
authors.forename: Saundra
authors.initials: S
authors.lastname: Buys
authors.forename: Richard B
authors.initials: RB
authors.lastname: Hayes
mesh_terms: D000236:Adenoma / Q000175:diagnosis* / Q000453:epidemiology*; D000368:Aged; D015992:Body Mass Index; D015179:Colorectal Neoplasms / Q000175:diagnosis* / Q000453:epidemiology*; D005260:Female; D020249:Hormone Replacement Therapy / Q000706:statistics & numerical data*; D006801:Humans; D008403:Mass Screening / Q000706:statistics & numerical data*; D008875:Middle Aged; D017584:Reproductive History; D012812:Sigmoidoscopy; D011795:Surveys and Questionnaires; D014481:United States / Q000453:epidemiology