The National Cancer Institute's (NCI) DES Combined Cohort Follow-up Study was formed in 1992. NCI researchers brought together a large group of mothers and their children who had been exposed to DES, as well as a group of similar (in age, medical history, etc.), but unexposed persons. NCI recruited for this study primarily from previously studied groups and their family members. These cohort groups were followed over a long period of time. For this reason, new people cannot be added to the study.
Following is a list and brief description of the DES Cohort Studies.
- Diethylstilbestrol Adenosis Project (DESAD) - The DESAD began in 1974 at Baylor College of Medicine, Gundersen Clinic, Massachusetts General Hospital, the Mayo Clinic, and the University of Southern California. The DESAD, the largest DES cohort, included 4,014 DES Daughters and 1,033 unexposed women. Exposed women had documented evidence of DES exposure through review of prenatal records or by physician referral. The DESAD was assembled to conduct studies to determine if DES Daughters were at an increased risk for health problems related associated with their exposure to DES (Labarthe, 1978).
- DES Mothers Study - The DES Mothers Study began in 1980. The participant group (cohort) included approximately 3,000 women exposed to DES while pregnant and 3,000 unexposed women. These participants had delivered babies during 1940-1960 at Boston Lying-In Hospital, the Mayo Clinic, Dartmouth Medical School, and a private practice in Portland, Maine. Exposure status was determined through review of medical records. The cohort was created to determine if women exposed to DES during pregnancy were at increased risk for cancer (Greenberg, 1984).
- Mayo Clinic Sons Study - The Sons Study included approximately 800 men exposed to DES before birth (in the womb) and 600 unexposed men. This cohort was identified by review of medical records of women who gave birth at Mayo Clinic hospitals (Leary, 1984).
- Connecticut Mothers Study - The participants included women who delivered babies during 1946-1965 at medical offices in Fairfield and New Haven Counties, Connecticut. The participants included 1,706 DES-exposed mothers and 1,405 unexposed mothers. The participants are now included in the DES Combined Cohort Studies (Hadjimichael, 1984).
- Dieckmann Cohort - Participants in the group, assembled in 1974 to study DES-related health risks, included approximately 800 women exposed to DES while pregnant and 800 unexposed mothers; approximately 400 women exposed to DES before birth (in the womb) and 400 women in a control group; and approximately 400 men exposed to DES before birth and 400 unexposed men. The 1974 group comprised the second Dieckmann cohort; the first included mothers who were participants in a study at the University of Chicago in the early 1950s. Results based on the initial study indicated that DES was not effective in preventing miscarriages (Dieckmann, 1953).
- British Research Medical Council (BRMC) Study - Participants included pregnant diabetic women enrolled in clinical trial and DES Daughters and DES Sons identified through follow-up study, for a total of 151 participants (79 DES-exposed and 72 unexposed people) (Reid, 1955).
- British Randomized Trial - A group assembled to study DES-related health effects. Participants included women exposed to DES during pregnancy and men and women exposed before birth (in the womb). The DES-exposed group included 379 mothers, 144 daughters, and 177 sons. A control group of unexposed included 371 mothers, 170 daughters, and 163 sons (Guisti, 1995).
- Registry for Research on Hormonal Transplacental Carcinogenesis - The Registry was established at Massachusetts General Hospital in 1971 to track the incidence of clear cell adenocarcinoma (CCA) of the vagina or cervix. The registry originally numbered 21 cases; however, by 2002, approximately 750 cases had been recorded at the registry. Most of the information on treatment outcome and recurrence rates of CCA has come from the study of patients in the Registry. The registry is now located at the University of Chicago (Department of Obstetrics and Gynecology, The University of Chicago, 5841 South Maryland Avenue, Mail Code 2050, Chicago, IL 60637. Phone: 773-702-6671. Fax: 773-702-5161) (Herbst, 1972).
Researchers continue to monitor the health status of 15,000 members of the combined cohort study. Many of the health problems being monitored are health problems that may be influenced by exposure to DES before birth (in the womb). These health problems include breast cancer in women, testicular cancer in men, and the potential interaction of hormone replacement therapy with DES exposure.
Researchers also are monitoring rates of health problems that appear to have no relationship to DES exposure (such as heart disease and diabetes). Scientists have no hypothetical or other reason to believe there is any link between DES and these diseases. These studies are being done to evaluate the overall health of DES-exposed persons.
The health risks associated with DES exposure change over a person's lifetime. Consequently, research is ongoing to learn how health risks change as DES-exposed persons age.
For instance, DES Daughters who are still in their 30s may not have yet faced their risk for infertility, ectopic pregnancy, or other pregnancy complications. Older DES Daughters and their mothers could be just reaching the stage of life where they must make an informed decision about estrogen replacement therapy. Age of DES-exposed persons is particularly relevant when thinking about DES exposure and cancer risk. Most cancer diagnoses do not begin to emerge until people are well into their fifth decade of life. Men and women who were exposed to DES before birth (in the womb) are just beginning to reach that age. Only continued research will show whether people who were exposed to DES before birth are at an increased risk for breast cancer, prostate cancer, and other diseases.
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