Source Newsroom: Society of Gynecologic Oncology
New Study Released Today Supports Belief That Combining Estrogen with A Progestin Decreases Risk of Endometrial Cancer Among Menopausal Women
CHICAGO, April 14, l998 -- Menopausal women who combine estrogen with progestin decrease their risk of developing endometrial cancer. This is the conclusion reached by researchers conducting 22- year retrospective study of women 45 years of age and older in the Southern California Kaiser Foundation Health Plan, and reported in the March l998 edition of Gynecologic Oncology, the premier publication of the Society of Gynecologic Oncology (SGO).
The study authors are Harry K. Ziel, MD Department of Obstetrics and Gynecology, Kaiser Permanente Medical Center, William D. Finkle, Ph.D., Consolidated Research, Inc., and Sander Greenland, Dr.P.H., C.Stat., Department of Epidemiology, University of California, Los Angeles School of Public Health.
Research Objectives: Previous epidemiological studies have documented that the use of unopposed estrogen is associated with an increased risk of endometrial cancer. To test the hypothesis that estrogen, combined with a progestin, reduces the risk of endometrial cancer, the researchers conducted a large retrospective review of the health plan registry.
Methodology: The researchers analyzed estrogen and progestin use, and the relationship of the combined therapies to the risk of endometrial cancer. The study spanned a 22-year period, beginning in 1971 and ending in 1993.
The research team estimated the annual incidence of endometrial cancer among Kaiser Health Plan participants by dividing the number of cases that were reported to Kaiser's Tumor Registries by the number of females aged 45 and older. The amount of conjugated estrogen and progesterone tablets was determined by dividing the number of tablets dispensed by the pharmacy by the number of female enrollees over age 45. (The progesterone tablet medroxyprogesterone, was used.)
The data are ecologic, i.e., they do not directly link drug usage to other medical events (such as hysterectomies) affecting study participants. Since individual records were not available on the women, no data were obtained about medical histories. Analyses were limited to a regression model of the annual incidence of estrogen and progestin usage per woman immediately prior to the incidence of endometrial cancer.
Results: The lowest endometrial cancer incidence (1991 through 1993) coincided with the highest estrogen prescriptions. This contradicts the generally accepted view that the use of estrogen increases the risk for endometrial cancer. The paradox is resolved, however, when the fact that medroxyprogesterone use increased during this same time period is taken into account.
Conclusion: The data are consistent with the hypothesis that the risk of consuming conjugated estrogens combined with progestins is much less than risk from using conjugated estrogens alone. The researchers recommend further research using a case-control study.
"The study done by Dr. Ziel and his colleagues underscores how important continued long-term research is for women -- especially the effects of hormones and their relation to reproductive cancer," said Karl C. Podratz, MD, Ph.D., Professor and Department Chair at the Mayo Clinic, and President of the Society of Gynecologic Oncology. Dr. Podratz added, "This information is good news to women who have been using combined estrogen and progesterone hormone replacement therapy."
The Society of Gynecologic Oncologists (SGO) is the world's largest medical organization dedicated to the prevention, detection, and cure of female cancers. More information about gynecologic cancer is available on the Internet at www.sgo.org or www.wcn.org. Gynecologic Oncology is published by Academic Press.
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Editor's Note: For the full abstract of this study or questions, contact Johanna Spangenberg at (703) 527-7424.