Review
Postmenopausal hormone therapy and the risk of colorectal cancer: a review and meta-analysis

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Abstract

PURPOSE: 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).

CONCLUSION: Observational studies suggest a reduced risk of colorectal cancer among women taking postmenopausal hormones. There is biologic evidence to support this association.

Section snippets

Methods for quantitative overview

Through computer searches of the MEDLINE database and review of references, we sought to identify all English-language articles with quantitative data regarding the effect of postmenopausal hormone use on the risk of colorectal cancer in women. MEDLINE searches encompassed the years between January 1966 and September 1998; we identified articles using the medical-subject-headings terms “colorectal, colon, and rectal neoplasm” or textword terms “colorectal, colon, and rectal cancer” and the

Colon cancer and ever use of postmenopausal hormones

The RR of colon cancer associated with “ever” use of any postmenopausal hormone therapy, as compared with “never” users, ranged from 0.0 to 1.3 (Table 1). Thirteen of the 18 studies reported lower risks of colon cancer for ever users of postmenopausal hormones than nonusers. The summary RR was 0.80 (95% CI, 0.74 to 0.86). This point estimate was included in the CIs of all but two of the individual studies. However, there was significant heterogeneity among the studies (P = 0.02). When we

Discussion

Observational epidemiologic evidence suggests that there is a decreased risk of colorectal cancer among postmenopausal hormone users. We found a 20% reduction in cancer of the colon and a 19% reduction in cancer of the rectum among women who had ever used postmenopausal hormones compared with never users. The observed decrease was strongest among women currently taking postmenopausal hormones, in whom the risk of colorectal cancer was 34% lower than in never users. However, we found no effect

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  • Cited by (0)

    Supported by Research Grants CA 40356 and CA 42182 from the National Institutes of Health (FG, MJS); Grant AG13482 from the National Institutes of Health (FG); and a Young Scholars Award from the Ellison Medical Foundation (FG).

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