Age-incidence and risk of diethylstilbestrol-related clear cell adenocarcinoma of the vagina and cervix.

This study was based on cases accessioned in the Registry of Clear Cell Adenocarcinoma of the Genital Tract in Young Females to ascertain the incidence of diethylstilbestrol (DES)-related cancers by age and year of birth. For accuracy in estimating the size of the reference population for the incidence rates, calculations were restricted to 127 white residents of the United States who were exposed prenatally to DES or other nonsteroidal synthetic estrogens. The disease is exceedingly rare prior to age 14 when the incidence rate begins to rise rapidly. The incidence peaks at age 19 (median 19.2 years) and then drops precipitately. Thus, DES-related clear cell adenocarcinoma is unusual in that nearly all cancers have been diagnosed in a narrow age range of 10 years (14 to 23 years). Women born in 1951 to 1953 have higher incidence rates than those born in the previous or subsequent three-year period. This suggests that the prevalence of pregnancy-related use of DES was at a peak in the early 1950's. The cumulative risk of this type of genital cancer, through age 24, for DES-exposed female subjects is estimated to be in the range of 0.14 to 1.4 per thousand. The wide limits are due to the fact that the number of young women exposed is not known precisly. The low risk of disease and the narrow age range of the cases, relative to the long latency period, suggest that DES is an incomplete carcinogen. Other factors, possibly related to puberty, may be involved in the causation of this disease.