Estrogen May Reduce Colorectal Cancer Risk in Postmenopausal Women

Hormone replacement therapy may reduce the risk of colorectal cancer in women, according to new results of a meta-analysis presented at the North American Menopause Society meeting.

From the first quantitative review of 18 epidemiologic studies done in the United States and Europe of the effects of hormone replacement therapy on colorectal cancer rates in postmenopausal women, Harvard University researcher Meir Stampfer, md, drph, found that women currently taking estrogen had up to a 34% reduction in colorectal cancer rates compared with women who had never used hormones. Overall, there was a 20% reduction in the rate of colon cancer and a 15% reduction in the rate of rectal cancer among women who had taken estrogen at some point in their lives. “Our analysis strongly suggests estrogen replacement therapy can help reduce the risk of colorectal cancer,” said Stampfer.

“This research finding, although provocative, does not eliminate the need for colorectal cancer screening, which currently is the only proven way to prevent colorectal cancer,” said Randall W Burt, md, professor of medicine, University of Utah; program head, Huntsman Cancer Institute; and a member of the AGA governing board. “Colorectal cancer screening for postmenopausal women should be taken as seriously as mammograms and Pap smears.”

Possible Mechanism

Although researchers are not certain how estrogen affects the colon, it is possible that it alters the production of bile acids that aid digestion in the colon and seem to be important for colorectal cancer. In addition, estrogen interacts with estrogen-specific receptors that line the colon and could suppress the growth of abnormal cells.

Both Drs. Burt and Stampfer agree that further studies are needed to determine why estrogen may protect postmenopausal women against colorectal cancer and to shed light on how physicians might prevent the disease in the future.