Offspring of women exposed in utero to diethylstilbestrol (DES): a preliminary report of benign and malignant pathology in the third generation, 2008
Animal studies suggest that prenatal exposure to the synthetic estrogen diethylstilbestrol (DES) causes epigenetic changes that may be transmitted to the next generation. Specifically, these studies show an elevated incidence of reproductive tumors in the female offspring of prenatally-exposed mice.
We assessed cancer and benign pathology diagnoses occurring in the offspring of women whose prenatal exposure to DES (or lack of exposure) was verified by medical record. Our data arose from 2 sources: the mothers’ reports of cancers occurring in 8216 sons and daughters, and pathology-confirmed cancers and benign diagnoses self-reported by a subset of 793 daughters.
Although statistical power is limited, our data are consistent with no overall increase of cancer in the sons or daughters of women exposed in utero to DES. Based on pathology-confirmed diagnoses reported by the daughters, we saw no association between DES and risk of benign breast disease or reproductive tract conditions. Based on 3 cases, the incidence of ovarian cancer was higher than expected in the daughters of women exposed prenatally to DES.
Our data do not support an overall increase of cancer risk in the sons or daughters of women exposed prenatally to DES, but the number of ovarian cancer cases was greater than expected. While preliminary, this finding supports continued monitoring of these daughters.
In 2001, the NCI assembled the third-generation cohort, consisting of the adult daughters (≥18 years of age) of DES-exposed and unexposed second-generation women.37 A review of parity records at all 5 study centers identified 763 exposed and 577 unexposed mothers of 966 exposed and 815 unexposed age-eligible daughters. About half of the mothers, 414 (54%) of the exposed and 297 (52%) of the unexposed, gave permission to contact 515 (53%) exposed and 383 (47%) unexposed daughters. The questionnaires, which queried daughters for hormonal and reproductive information, screening histories, and medical events (including gynecologic biopsies, breast biopsies, and cancer diagnoses), were returned by 793 (88%) of 898 daughters, including 463 (90%) exposed and 330 (86%) unexposed. Pathology reports were obtained to verify self-reported diagnoses and biopsies. A study-related review of histology slides confirmed 1 of 2 reported cases of borderline ovarian cancer. Slides were unavailable for the second case, which involved metastatic disease.
The confirmation of cancers occurring in the subset of adult daughters participating in the third-generation study was excellent. Of the 8 self-reported cancers, 7 (5 exposed, 2 unexposed) were confirmed by pathology; consent was not obtained to confirm a melanoma reported by an unexposed woman. For other conditions, confirmation of benign biopsies was reasonably good, generally exceeding 60%.
DES Follow-up Study Summary
Studies have shown a slightly increased risk of breast cancer in women who were given Diethylstilbestrol (DES) while they were pregnant. Their daughters, who were exposed to DES prenatally (before they were born), have an elevated risk of reproductive tract conditions, including a rare vaginal cancer. A question now being studied is whether DES health effects can be passed from the prenatally exposed women to their offspring (intergenerational transmission).
Studies in mice suggest that intergenerational transmission of DES health effects may be possible. Recent evidence indicates that prenatal exposure to DES may cause changes in the behavior of genes that influence hormones and the development of the female reproductive tract. These changes in gene behavior may be passed on to the next generation. Evidence for intergenerational transmission comes from mouse studies showing a higher number of reproductive tract tumors in the daughters of prenatally exposed female mice. We used the DES Follow-up Study data to assess whether cancer was more common in the offspring of women who were prenatally exposed to DES. Cancers affecting these offspring (the third generation) were identified using two approaches. First, we asked women participating in the DES Follow-up Study to report cancers diagnosed in their 8,216 third generation sons and daughters. Second, we asked 793 third generation daughters participating in the Third Generation Study to tell us about their cancers. We also asked the third generation daughters to tell us about their reproductive tract and breast biopsies. Next we confirmed the reported biopsies and cancers by checking the medical records of these third generation daughters.
Our results did not show an overall increase of cancer in the sons or in the daughters of prenatally DES-exposed women. However, based on only three cases, the number of ovarian cancers was higher than expected in the daughters of women exposed prenatally to DES. Because of the small number of cases, this result must be considered preliminary. The association may be a chance finding or may be due to the way in which the data were reported or collected. We did not find an association between DES and benign breast disease or reproductive tract conditions, but most of the women are too young for a meaningful assessment of these outcomes. Further follow-up is needed to assess whether prenatal DES exposure can affect the third generation in humans.
DES DIETHYLSTILBESTROL RESOURCES