Since the discovery of an increased cancer risk among DES Daughters in 1971, some researchers have investigated whether men exposed to DES before birth (in the womb), known as DES Sons, also have an increased risk of cancer. Researchers hypothesized that DES exposure could increase the risk for testicular cancer because prenatal exposure to abnormal levels of other types of estrogen have been associated with this cancer. Previous studies of the relationship between exposure to DES before birth and an increased risk of testicular cancer were inconclusive. Some studies showed an increased rate of testicular cancer for DES Sons compared with unexposed men, and other studies indicated no differences.

The authors of this study conducted a follow-up study comparing the cancer rates of DES Sons with the cancer rates of unexposed men. A total of 2,759 men participated in the study, including 1,365 DES-exposed men and 1,394 unexposed men. The study included a review of death certificates for 48 men who died during 1978-1994 from any type of cancer. Researchers also reviewed the men's medical histories for 1978-1994, including any cancer risk factors (such as smoking or a previous history of cancer). The researchers compared the number of cancer cases in the DES-exposed men with the number of cancer cases in unexposed men. These rates also were compared with cancer rates for men in the general population (whose DES exposure status was not known).

The researchers found that the overall rate of cancer in DES Sons was not higher than the rate of cancer in the general population. However, the researchers did find that slightly more cases of testicular cancer occurred in DES-exposed men than in unexposed men, or than would be expected in the general population. Seven DES Sons were diagnosed with testicular cancer at ages 23-41, compared with two unexposed men ages 28 and 40.

Even with the higher rates of testicular cancer among DES Sons, the study did not prove an association between exposure to DES before birth and testicular cancer. The number of DES Sons diagnosed with testicular cancer was not large enough to prove an association. In other words, the higher rate of testicular cancer among DES Sons could have resulted from chance rather than exposure to DES. In addition, researchers did not know the amount of DES taken by mothers of the DES Sons in the study, or the timing of DES prescriptions during pregnancy. Dosage and timing could result in different cancer risks.

Citation: Strohsnitter WC, Noller KL, Hoover RN, Robboy SJ, Palmer JR, et al. Cancer risk in men exposed in utero to diethylstilbestrol. Journal of the Natl Cancer Inst 2001;93:545-51.