title: Conjugated equine estrogens and colorectal cancer incidence and survival: the Women's Health Initiative randomized clinical trial.
abstract: BACKGROUND
  In separate Women's Health Initiative randomized trials, combined hormone therapy with estrogen plus progestin reduced colorectal cancer incidence but estrogen alone in women with hysterectomy did not. We now analyze features of the colorectal cancers that developed and examine the survival of women following colorectal cancer diagnosis in the latter trial.
  
  
  METHODS
  10,739 postmenopausal women who were 50 to 79 years of age and had undergone hysterectomy were randomized to conjugated equine estrogens (0.625 mg/d) or matching placebo. Colorectal cancer incidence was a component of the monitoring global index of the study but was not a primary study endpoint. Colorectal cancers were verified by central medical record and pathology report review. Bowel exam frequency was not protocol defined, but information on their use was collected.
  
  
  RESULTS
  After a median 7.1 years, there were 58 invasive colorectal cancers in the hormone group and 53 in the placebo group [hazard ratio, 1.12; 95% confidence interval (95% CI), 0.77-1.63]. Tumor size, stage, and grade were comparable in the two randomization groups. Bowel exam frequency was also comparable in the two groups. The cumulative mortality following colorectal cancer diagnosis among women in the conjugated equine estrogen group was 34% compared with 30% in the placebo group (hazard ratio, 1.34; 95% CI, 0.58-3.19).
  
  
  CONCLUSIONS
  In contrast to the preponderance of observational studies, conjugated equine estrogens in a randomized clinical trial did not reduce colorectal cancer incidence nor improve survival after diagnosis.
authors.affiliation: University of Arizona College of Medicine, Tucson, Arizona 85719, USA. ritenbau@email.arizona.edu
authors.forename: Cheryl
authors.initials: C
authors.lastname: Ritenbaugh
authors.forename: Janet L
authors.initials: JL
authors.lastname: Stanford
authors.forename: LieLing
authors.initials: L
authors.lastname: Wu
authors.forename: James M
authors.initials: JM
authors.lastname: Shikany
authors.forename: Robert E
authors.initials: RE
authors.lastname: Schoen
authors.forename: Marcia L
authors.initials: ML
authors.lastname: Stefanick
authors.forename: Vicky
authors.initials: V
authors.lastname: Taylor
authors.forename: Cedric
authors.initials: C
authors.lastname: Garland
authors.forename: Gail
authors.initials: G
authors.lastname: Frank
authors.forename: Dorothy
authors.initials: D
authors.lastname: Lane
authors.forename: Ellen
authors.initials: E
authors.lastname: Mason
authors.forename: S Gene
authors.initials: SG
authors.lastname: McNeeley
authors.forename: Joao
authors.initials: J
authors.lastname: Ascensao
authors.forename: Rowan T
authors.initials: RT
authors.lastname: Chlebowski
mesh_terms: D000368:Aged; D015179:Colorectal Neoplasms / Q000453:epidemiology*; D004311:Double-Blind Method; D004966:Estrogens, Conjugated (USP) / Q000008:administration & dosage*; D005260:Female; D006801:Humans; D015994:Incidence; D008875:Middle Aged; D010919:Placebos; D017698:Postmenopause; D016016:Proportional Hazards Models; D012307:Risk Factors; D016019:Survival Analysis; D014481:United States / Q000453:epidemiology
chemical_list: D004966:Estrogens, Conjugated (USP); D010919:Placebos