Postmenopausal hormone therapy and the risk of colorectal cancer: a review and meta-analysis.
OBJECTIVE
Colorectal cancer is the fourth most common cancer and the second leading cause of cancer death in the United States. Accumulating evidence indicates that postmenopausal hormone therapy may reduce the risk of colorectal cancer in women.


METHODS
Through MEDLINE computer searches (January 1966 to September 1998) and a review of references, we identified English-language articles with quantitative data on the relation of postmenopausal hormone therapy to colorectal cancer. We reviewed the studies and made summary estimates of relative risks (RR) by weighting the results of each study in proportion to its precision, using a general variance-based, fixed-effects model.


RESULTS
In our meta-analysis of 18 epidemiologic studies of postmenopausal hormone therapy and colorectal cancer, we found a 20% reduction [RR = 0.80, 95% confidence interval (CI), 0.74 to 0.86] in risk of colon cancer and a 19% decrease (RR = 0.81, 95% CI, 0.72 to 0.92) in the risk of rectal cancer for postmenopausal women who had ever taken hormone therapy compared with women who never used hormones. Much of the apparent reduction in colorectal cancer was limited to current hormone users (RR = 0.66, 95% CI, 0.59 to 0.74).


CONCLUSIONS
Observational studies suggest a reduced risk of colorectal cancer among women taking postmenopausal hormones. There is biologic evidence to support this association.
Grodstein
F
F
Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts 02115, USA.
Newcomb
P A
PA
Stampfer
M J
MJ
D018931:Antineoplastic Agents, Hormonal / Q000009:adverse effects; D015179:Colorectal Neoplasms / Q000453:epidemiology* / Q000517:prevention & control*; D004965:Estrogen Antagonists / Q000009:adverse effects; D015914:Estrogen Replacement Therapy; D005260:Female; D020249:Hormone Replacement Therapy / Q000706:statistics & numerical data*; D006801:Humans; D015994:Incidence; D017698:Postmenopause; D012306:Risk; D013629:Tamoxifen / Q000009:adverse effects; D014481:United States / Q000453:epidemiology
D018931:Antineoplastic Agents, Hormonal; D004965:Estrogen Antagonists; D013629:Tamoxifen