Research shows estrogen plus progestin cut postmenopausal women's colon cancer risk

March 04, 2004

CHAPEL HILL — In postmenopausal women, relatively short-term use of the hormones estrogen and progestin appears to cut the risk of colorectal cancer, a new multi-center national study shows.Among the small percentage of women in the study who developed the cancer, however, those who took the combined hormone treatment were diagnosed at a more advanced disease stage than those who took a placebo.

“These findings support wider implementation of bowel screening among postmenopausal women who are using hormone therapy,” authors of a report on the study concluded. “Current data are insufficient to support the use of estrogen plus progestin to reduce the risk of colorectal cancer in any population.

“Before therapy with estrogen plus progestin is used in any setting by postmenopausal women, all identified and emerging risks associated with these agents should be considered.”

Their report appears in the March 4 issue of the New England Journal of Medicine.

Investigators contributing to the study represent more than 40 medical centers, clinics and government agencies throughout the United States. Among the centers is the University of North Carolina at Chapel Hill, where public health and medical school faculty have been working with more than 1,500 women volunteers.

UNC faculty investigators are Drs. Gerardo Heiss, professor of epidemiology in the School of Public Health and principal investigator; Pamela Haines, associate professor of nutrition in the Schools of Public Health and Medicine; Carla Sueta, associate professor of medicine in the School of Medicine; and Ellen C. Wells, assistant professor of obstetrics and gynecology, also in the School of Medicine.

Across the country, researchers found 43 invasive colorectal cancers among subjects in the hormone group and 72 in the placebo group. Women in the first group, however, showed more cancerous lymph nodes and somewhat more advanced tumors than the others.

“In the current study, vaginal bleeding was more common among women in the hormone group than among those in the placebo group, and this factor may have delayed assessment and accounted for the higher incidence of advanced cancer in the hormone group,” the authors wrote.

“There is wide support for a policy of regular bowel screening for women 50 years of age or older,” they said. “Nevertheless, the experience in this group, in which only a minority of the participants underwent routine bowel screening, reflects that of the general population.”

The National Institutes of Health announced Tuesday (March 2) that it was stopping a related study of the effects of estrogen alone on postmenopausal women who had hysterectomies. That was because some of the same researchers found none of the hoped-for heart-related benefits after an average follow-up of almost seven years but did uncover a slight increase in the stroke risk among participants receiving the single hormone.

In July 2002, NIH halted its study of combined estrogen and progestin therapy after finding a small increase in breast cancer, heart attacks and stroke in treated women when compared with controls who did not take the combined hormones. The new paper is based on data from that investigation.

More than 16,600 postmenopausal women participated in that Women’s Health Initiative study, which the National Heart, Lung and Blood Institute sponsors. In all, more than 161,000 women are enrolled in either a set of hormone preventive health trials or a larger observational study involving no treatment. Those trials focus on ways to prevent heart disease, osteoporosis and the resulting fractures, and breast and colorectal cancer. WHI researchers nationwide also are continuing to evaluate the potential benefits of low-fat diets and calcium and vitamin D supplementation.

Most doctors now recommend against the combined therapy in the absence of strong menopause-related symptoms, saying the risks of estrogen plus progestin outweigh the benefits.

More recent findings provided new evidence that the combined hormone therapy boosted the risks of dementia and strokes in subjects while not improving what scientists call “global cognitive function” — how well or poorly the brain works.

Details about menopausal hormone therapy are available at www.nhlbi.nih.gov. The National Cancer Institute, the National Institute of Arthritis and Musculoskeletal and Skin Diseases, the National Institute on Aging and the Office of Research on Women’s Health also support the Women’s Health Initiative investigations.

Note: Heiss can be reached at (919) 962-3253.

This news release was researched and written by David Williamson, research editor for University News Services.

School of Public Health contact: Lisa Katz, (919) 966-7467

News Services contact: David Williamson, (919) 962-8596