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DES Follow-up Study Background

Timeline The National Cancer Institute (NCI) Combined DES Cohorts Follow-up Study is a nationwide research study following more than 21,000 women and men to learn as much as possible about the long-term health effects of DES exposure. The NCI study is the largest ongoing research study on long-term health and DES exposure. Five research centers in the United States carry out the DES Follow-up Study, coordinated by NCI. Leaders in DES research and education are responsible for the study and are dedicated to increasing scientific and medical knowledge about DES exposure. The research team includes physicians, epidemiologists, researchers, and DES advocates and educators. The following provides more background information about DES and the DES Followup Study.

The following provides more background information about DES and the DES Followup Study.

  What is DES
  Reasons to Study DES
  The History of DES Research at NCI
  NCI’s DES Follow-up Study
      DESAD Cohort
      Women’s Health Study Cohort
      Mayo Clinic Cohort
      Dieckmann Cohort
      Horne Cohort
  How the DES Follow-up Study is Conducted
  Priorities and Challenges of the DES Follow-up Study
  Scientific researchers, center coordinators and DES advocates
  1994-2011 Questionnaires

What is DES?

Diethylstilbestrol (DES) is a non-steroidal estrogen, and the first estrogen pill. It was produced in 1938 and was widely used from the mid-1940s until the early 1970s as a treatment for women who were at risk of miscarriages. It is estimated that millions of Americans (mothers, daughters, and sons) may have been exposed to DES. In 1971, data demonstrated a connection between a mother’s use of DES during pregnancy and the occurrence of cancer of the vagina in her daughters. Subsequently, DES has been associated with several other health effects, including an increased frequency of problems of the reproductive tract, changes in the tissue of the vagina, infertility and poor pregnancy outcomes in daughters.

Reasons to Study DES

The most important reason to study DES is to provide DES-exposed people and medical professionals with information about the long-term health effects of DES exposure.

The study is also an important source of scientific information. DES is often used as a way of studying how chemicals that act like or interfere with hormones in the body affect health. Although numerous cancer-causing agents are known to pass from the placenta to the fetus in animals, DES is unique because it is the only agent known to do the same in humans.

Finally, the study of DES may aid in understanding the effects of hormones, in general, during the development of the fetus.

The History of DES Research at NCI

The NCI study is funded by Congress because of passage of the DES Research and Education legislation.

Congress has passed two bills requiring research on DES exposure, and two National Institutes of Health (NIH)-sponsored workshops on DES were held in 1992 and 1999 to make research recommendations. These recommendations included the following:

Continue to monitor the people participating in studies of DES for cancer risk, particularly among daughters as they approach menopause and among DES-exposed sons;

Assess the impact of and risks associated with exposure to other hormones such as hormone replacement therapy in DES-exposed mothers and daughters;

Study whether DES-exposed women and men will develop non-reproductive conditions.

NCI’s DES Follow-up Study

In 1992, NCI, together with researchers at five research centers, began a long-term study of individuals exposed to DES. Participants were initially drawn from eight different medical centers and consisted of five individual cohorts (groups of people being studied). These cohorts are the DESAD cohort, Women’s Health Study cohort, Mayo Clinic cohort, Dieckmann cohort, and Horne Cohort. In order for the study findings to be valid, enrollment in the study is limited to participants who have been part of existing cohorts. Currently, it is not possible for the DES Follow-up Study to accept new participants. Five cohorts (groups of people being studied) make up the DES Follow- Up Study.

How the DES Follow-up Study is Conducted

The DES Follow-Up Study participants are sent questionnaires requesting information about their recent health history. In 1994, 1997 and 2001, questionnaires were mailed to or telephone interviews conducted with participants in all the cohorts, and deaths were identified. Approximately two-thirds of the interviews were completed through the mail and one-third by telephone. Information on diseases such as cancer, benign breast and gynecologic tumors, precancerous conditions of the cervix, autoimmune diseases (like rheumatoid arthritis), psychiatric disorders, and genito-urinary conditions (such as epidydimal cysts) among the sons was collected. Information was collected also on general cancer risk factors and known breast, ovarian, and endometrial cancer risk factors, in addition to demographic variables (e.g., age, education), and health screening behaviors. This information has been and continues to be analyzed statistically to understand the relationship between DES and health outcomes. This is done by comparing the occurrence of disease in participants who were exposed to DES with those who were not exposed to DES.

Priorities and Challenges of the DES Follow-up Study

Our primary goal is to measure new cases of cancer and deaths from cancer, especially cancers of the breast and reproductive system. We also continue to assess a range of possible health effects related to DES exposure, monitoring for yet unanticipated health risks. Finally, we evaluate doing more detailed studies of specific DES-related conditions. One of the major problems in studying DES is establishing a cohort with proof of exposure. DES exposure typically occurred up to 30 or more years ago and most prenatal records have been destroyed, obstetricians have retired or are deceased, and mothers are deceased or do not recall their drug exposures from such a long time ago. Therefore, the DES Follow-up Study, which has followed the largest cohort of documented DES exposed people over time, represents the only remaining opportunity to study DES health effects on a population followed over a period of time.

1994-2011 Questionnairs

2011Women's QuestionnairMen's Questionnair
2006Women's QuestionnairMen's Questionnair
2001Women's QuestionnairMen's Questionnair
1997Women's QuestionnairMen's Questionnair
1994Women's QuestionnairMen's Questionnair

DES Researchers

Scientific researchers, center coordinators and DES advocates