title: Estrogen and colorectal cancer incidence and mortality.
abstract: BACKGROUND
  The preponderance of observational studies describe an association between the use of estrogen alone and a lower incidence of colorectal cancer. In contrast, no difference in the incidence of colorectal cancer was seen in the Women's Health Initiative (WHI) randomized, placebo-controlled trial with estrogen alone after a mean intervention of 7.1 years and cumulative follow-up of 13.2 years. This study extends these findings by providing detailed analyses of the effects of estrogen alone on the histology, grade, and stage of colorectal cancer, relevant subgroups, and deaths from and after colorectal cancer.
  
  
  METHODS
  The WHI study was a randomized, double-blind, placebo-controlled trial involving 10,739 postmenopausal women with prior hysterectomy. Participants were assigned to conjugated equine estrogen at 0.625 mg/d (n = 5279) or a matching placebo (n = 5409). Rates of colorectal cancer diagnoses and deaths from and after colorectal cancer were assessed throughout the study.
  
  
  RESULTS
  Colorectal cancer rates in the estrogen-alone and placebo groups were comparable: 0.14% and 0.12% per year, respectively (hazard ratio [HR], 1.13; 95% confidence interval [CI], 0.83-1.58; P = .43). Bowel screening examinations were comparable between the 2 groups throughout the study. The grade, stage, and location of colorectal cancer did not differ between the randomization groups. There were more colorectal cancer deaths in the estrogen-alone group (34 [0.05%] vs 24 [0.03%]; HR, 1.46, 95% CI, 0.86-2.46; P = .16), but the difference was not statistically significant. The colorectal cancer incidence was higher for participants with a history of colon polyp removal in the estrogen-alone group (0.23% vs 0.02%; HR, 13.47; nominal 95% CI, 1.76-103.0; P < .001).
  
  
  CONCLUSIONS
  The use of estrogen alone in postmenopausal women with prior hysterectomy does not influence the incidence of colorectal cancer or deaths from or after colorectal cancer. A possibly higher risk of colorectal cancer in women with prior colon polyp removal who use estrogen alone requires confirmation.
authors.affiliation: Karmanos Cancer Institute, Department of Oncology, Wayne State University, Detroit, Michigan.|Population Studies and Prevention Program, Karmanos Cancer Institute, Wayne State University, Detroit, Michigan.
authors.forename: Sayeh
authors.initials: S
authors.lastname: Lavasani
authors.affiliation: Los Angeles Biomedical Research Institute, Harbor-UCLA Medical Center, Torrance, California.
authors.forename: Rowan T
authors.initials: RT
authors.lastname: Chlebowski
authors.affiliation: Division of Public Health Sciences, Fred Hutchinson Cancer Research Center, Seattle, Washington.
authors.forename: Ross L
authors.initials: RL
authors.lastname: Prentice
authors.affiliation: Population Studies and Prevention Program, Karmanos Cancer Institute, Wayne State University, Detroit, Michigan.|Department of Pathology, Wayne State University, Detroit, Michigan.
authors.forename: Ikuko
authors.initials: I
authors.lastname: Kato
authors.affiliation: Department of Social and Preventive Medicine, University at Buffalo, Buffalo, New York.
authors.forename: Jean
authors.initials: J
authors.lastname: Wactawski-Wende
authors.affiliation: Department of Preventive Medicine, University of Tennessee Health Science Center, Memphis, Tennessee.
authors.forename: Karen C
authors.initials: KC
authors.lastname: Johnson
authors.affiliation: Division of Public Health Sciences, Fred Hutchinson Cancer Research Center, Seattle, Washington.
authors.forename: Alicia
authors.initials: A
authors.lastname: Young
authors.affiliation: Division of Public Health Sciences, Fred Hutchinson Cancer Research Center, Seattle, Washington.
authors.forename: Rebecca
authors.initials: R
authors.lastname: Rodabough
authors.affiliation: Department of Medicine, University of California Irvine, Irvine, California.
authors.forename: F Allan
authors.initials: FA
authors.lastname: Hubbell
authors.affiliation: University of Liverpool, Liverpool, United Kingdom.
authors.forename: Ali
authors.initials: A
authors.lastname: Mahinbakht
authors.affiliation: Karmanos Cancer Institute, Department of Oncology, Wayne State University, Detroit, Michigan.|Population Studies and Prevention Program, Karmanos Cancer Institute, Wayne State University, Detroit, Michigan.
authors.forename: Michael S
authors.initials: MS
authors.lastname: Simon
mesh_terms: D000230:Adenocarcinoma / Q000453:epidemiology*; D000368:Aged; D015179:Colorectal Neoplasms / Q000453:epidemiology*; D004311:Double-Blind Method; D015914:Estrogen Replacement Therapy / Q000379:methods; D004967:Estrogens / Q000627:therapeutic use; D004966:Estrogens, Conjugated (USP) / Q000627:therapeutic use*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D015994:Incidence; D008875:Middle Aged
chemical_list: D004967:Estrogens; D004966:Estrogens, Conjugated (USP)
keywords: colorectal cancer; estrogen; incidence; mortality; postmenopausal women