Estradiol and Colon Cancer

Several epidemiologic studies have found that estradiol replacement therapy (ERT) in postmenopausal women decreases their risk of developing colon or colorectal cancer by up to 50%:

Epidemiology, 1991

Among 118,404 female registered nurses who responded to a mailed questionnaire and had no history of cancer in 1976, 191 colon cancers and 49 rectal cancers were diagnosed during 8 years of follow-up.

Use of postmenopausal estrogens was associated with a reduced risk of colorectal cancer (Relative Risk = 0.5, 95% CL: 0.3-1.0).

Chute CG, et al: A prospective study of reproductive history and exogenous estrogens on the risk of colorectal cancer in women. Epidemiology 2:201-207, 1991

Cancer Causes and Control, 1992

The results indicate that postmenopausal hormone-replacement therapy might reduce the risk of colorectal cancer.

(age-adjusted relative risk [RR] = 0.4, 95% confidence interval = 0.2-0.9). Adjustments for diet, body mass, and physical activity had little influence on the results.

Gerhardsson de Verdier M et al: Reproductive factors, exogenous female hormones, and colorectal cancer by subsite. Cancer Causes Control 3:355-360, 1992

Cancer Research, 1989

Menopausal estrogen use was found to protect against development of large bowel cancer with an odds ratio of 0.6 (95% CI, 0.33-0.99). Adjusting for age at diagnosis, parity, hysterectomy, oophorectomy, and cholecystectomy resulted in an adjusted odds ratio of 0.5 (95% CI, 0.27-0.90).

These data support the hypothesis that postmenopausal hormone replacement may decrease the risk of large bowel cancer in women.

Fumer SE, et al: A case-control study of large bowel cancer and hormone exposure in women. Cancer Res 49:4936-4940, 1989

The most extensive study on estrogen vs. colon cancer was published in 1995 in the Journal of the National Cancer Institute:

Estrogen replacement therapy and risk of fatal colon cancer in a prospective cohort of postmenopausal women: The present study attempts a definitive analysis of the relationship between fatal colon cancer and use of Estrogen Replacement Therapy among women in a large prospective study of adults in the United States.

Methods: Women were selected from the 676,526 female participants in Cancer Prevention Study II (CPS-II), a prospective mortality study of about 1.2 million men and women. After 7 years of follow-up, 897 colon cancer deaths were observed in a cohort of 422,373 postmenopausal women who were cancer-free at study entry.

Results: Women who had at some point used Estrogen Replacement Therapy had significantly decreased risk of fatal colon cancer (Relative Risk = 0.71; 95% confidence interval [CI] = 0.61-0.83). The reduction in risk was strongest among current users (RR = 0.55; 95% CI = 0.40-0.76), and there was a significant (P = .0001) trend of decreasing risk with increasing years of use: Women who used estrogen for 1 year or less had a Relative Risk of 0.81 (95% CI = 0.63-1.03), while users of 11 years or more had an RR of 0.54 (95% CI = 0.39-0.76). These associations were not altered in multivariate analyses controlling for other risk factors.

Conclusions: In our data, estrogen therapy, particularly recent and long-term use, was associated with a substantial decrease in risk of fatal colon cancer. These results were consistent with several published studies suggesting a protective role of estrogen replacement therapy in the development of colorectal cancer.

J Natl Cancer Inst. 1995 Apr 5;87(7):517-23.

Cancer Causes and Control, 1992

The results indicate that postmenopausal hormone-replacement therapy might reduce the risk of colorectal cancer.

(age-adjusted relative risk [RR] = 0.4, 95% confidence interval = 0.2-0.9). Adjustments for diet, body mass, and physical activity had little influence on the results.

Gerhardsson de Verdier M et al: Reproductive factors, exogenous female hormones, and colorectal cancer by subsite. Cancer Causes Control 3:355-360, 1992