In a study conducted in Germany and published in the British Journal of Cancer, use of postmenopausal hormones decreased the risk of colorectal cancer in women. In contrast to several previous studies, however, being overweight increased the risk of colorectal cancer only among women who had never used postmenopausal hormones.
Colorectal cancer is the second leading cause of cancer-related deaths in the U.S. The disease develops in the colon (the longest part of the large intestine) or the rectum (the last several inches of the large intestine). It may start as a precancerous growth known as an adenomatous polyp or adenoma.
Previous studies have suggested that postmenopausal hormone therapy with combined estrogen plus progestin reduces the risk of colorectal cancer. While the health risks of postmenopausal hormone use appear to outweigh this benefit, researchers continue to explore the relationship between postmenopausal hormone use and colorectal cancer risk.
One of the questions that has interested researchers is whether use of postmenopausal hormones influences the relationship between body weight and colorectal cancer risk. For example, some studies have reported that being overweight increases the risk of colorectal cancer, but only among women who use postmenopausal hormones. Other studies have reported that being overweight increases colorectal cancer risk among both users and nonusers of postmenopausal hormones.
To evaluate the relationships among postmenopausal hormone use, weight, and risk of colorectal cancer in Germany, researchers conducted a study among 208 postmenopausal women with colorectal cancer and 246 postmenopausal women without colorectal cancer.
Weight was assessed using the body mass index (BMI). BMI involves a comparison of weight to height (weight in kilograms divided by height in meters squared). A BMI between 18.5 and 24.9 is generally considered healthy, a BMI between 25 and 29.9 is considered overweight, and a BMI of 30 or higher is considered obese.
- Women who had ever used postmenopausal hormones were roughly 60% less likely to develop colorectal cancer than women who had never used postmenopausal hormones.
- Among women who had never used postmenopausal hormones, those who had a BMI of 27 or greater were significantly more likely to develop colorectal cancer than those who had a BMI of less than 23.
- Among women who had ever used postmenopausal hormones, BMI was not significantly linked with risk of colorectal cancer.
The finding that postmenopausal hormone use reduces the risk of colorectal cancer in women is consistent with several previous studies. The finding that excess body weight increased the risk of colorectal cancer only among women who had never used postmenopausal hormones is not consistent with most previous studies, and requires further study.
 Rossouw JE, Anderson GL, Prentice RL et al. Risks and benefits of estrogen plus progestin in healthy postmenopausal women: principal results from the Women’s Health Initiative randomized controlled trial. JAMA. 2002; 288:321-33
 Hoffmeister M, Raum E, Winter J, Chang-Claude J, Brenner H. Hormone replacement therapy, body mass, and the risk of colorectal cancer among postmenopausal women from Germany. British Journal of Cancer. 2007;97:1486-1492.