The Story Behind Clear Cell Cancer
In 1971 scientists established the link between exposure to DES before birth
and a rare cancer, called clear cell adenocarcinoma (adeno-car-ci-no-ma)
of the vagina in young women. This cancer is called clear cell cancer because
of the appearance of the cancer cells under a microscope. Before 1971, clear
cell cancer had been seen primarily in women older than the age of 60, and
then infrequently. The appearance of clear cell cancer in a group of young
women, most of whom had been exposed to DES before birth, was unprecedented
and established the link between DES exposure and clear cell cancer.
Exposure to DES has also been associated with a range of reproductive health
problems in some of the daughters, and reproductive tract abnormalities
in some of the sons of women who took DES during pregnancy. Women who were
prescribed DES during pregnancy may face a slightly increased risk of breast
cancer. Clear cell cancer is the health problem with the most clearly established
link to DES exposure before birth (in utero).
Since the link between DES and clear cell cancer was first discovered, about
600 cases have been reported to an international registry at the University
of Chicago. Although it is likely that additional cases have occurred, which
have not been reported, the Registry is the largest record of clear cell
cancer cases world-wide. Registry data indicates that not all women who
have had clear cell cancer were exposed to DES. Although there are some
unexposed patients, many women do not have proof of DES exposure because
medical records can not be located, or because their mother may not recall
taking DES.
In the last decade several DES daughters in their 30s and 40s have developed
clear cell cancer. It is important for DES daughters and their physicians
to be aware that there is no specific age after which the risk for clear
cell cancer is over. At this time the upper age limit for the development
of the cancer is unknown. Therefore, it is not known at this point if there
is an age at which DES daughters will be risk-free.
Market Sales of 25mg DES vs. Cases of
Clear Cell Cancer by Year of Diagnosis
This graph show the relationship between the sale of DES adn
the incidence of clear cell cancer 20 years later, by five year intervals.
The graph ends with DES sales in 1970 and reports of clear cell cancer in
1990, yet cases of clear cell cancer continue to occur in the 1990s. Reproduced
with the permission of: Dr. Shanna Swan, Berkeley, California 1994.
Understanding Clear Cell Cancer
Scientists do not know exactly how DES causes changes in fetal development
that affect an adult so many years after birth. It is thought that exposure
of the fetus to the estrogen DES, during the first three months of development,
changes the correct development of the structure and cells of the genital
organs. This in turn could lead to growth of glandular tissue that, with
other factors, may promote the development of cancer.
Why some DES daughters develop the cancer, while most do not, is unknown.
Development of clear cell cancer may have to do with the amount of DES taken,
and the time during the pregnancy that DES was taken.
The overall length of time the DES was used during the pregnancy may also
be a factor. Clear cell cancer may also be triggered when there is an increased
secretion of hormones within the body, as there is during puberty.
Although much remains unknown about the causes of clear cell cancer, the
years since 1971 have provided some information about the best way to treat
it. It is clear that a woman's chances for survival and her treatment options
are increased by regular screening for clear cell cancer by a physician
familiar with effects of DES on the cervix and vagina. Because clear cell
cancer is rare, if you are a woman who has been diagnosed with clear cell
cancer, it is important to seek medical advice and treatment from a gynecologist
who specializes in treating cancer (gynecologic oncologist) and is experienced
in treating clear cell cancer.
Women with clear cell cancer and their families must take an active role
to educate themselves about the disease and learn effective ways to discuss
treatment and outcome with their health care providers. There are resources
available that can help women with clear cell cancer adjust to the changes
that accompany treatment and survival (see page 42). DES consumer groups,
such as the DES Cancer Network, can offer information and emotional support.
Good communication within families, and professional counseling with a clinical
social worker, psychologist or psychiatrist can also be beneficial.
CLEAR CELL CANCER FACTS: A SUMMARY
Risk in DES daughter:...................1 in 1,000
Number of cases recorded:........Approximately 600
Years of diagnosis:...................1969-present
Age range at diagnosis:.............7-42 years old
Most frequent age at diagnosis:....15-27 years old
Upper age limit at diagnosis:..............Unknown
From the Registry for Research on Hormonal Carcinogenesis, University
of Chicago
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