Epidemiology of adenocarcinoma of the cervix.

There is general evidence that the incidence of adenocarcinoma of the cervix has been rising, particularly among younger women. The determinants of these trends, however, remain largely unknown. We have reviewed the epidemiology of adenocarcinoma of the cervix using descriptive data from cancer registration and clinical series and two main sources of analytical data: clinical studies comparing cervical adenocarcinoma (AC) and squamous carcinoma (SC) and formal case-control and cohort epidemiological studies. In both the United States and northern Europe there is evidence of the rising frequency of AC in absolute and relative terms as compared to SC. These trends are generally restricted to younger women: under-age-35 AC incidence approximately doubled from the early 1970s to the early 1980s. Available data, although scanty, consistently show that the frequency of cervical adenocarcinoma rises with the number of partners and with decreasing age at first intercourse, suggesting a potential role for sexually transmitted (viral) factors. In clinical series, nulliparity was reported more frequently in AC than in SC cases but an inconsistent association was found in three formal epidemiological studies. Similarities with the epidemiology of endometrial cancer are also suggested from the association with overweight, while a possible relation with hypertension and diabetes is based on clinical series only and hence more difficult to interpret. Thus, adenocarcinoma of the cervix appears to share epidemiological characteristics with both adenosquamous cancer of the cervix and adenocarcinoma of the endometrium, although uncertainties in classification and registration leave several questions unanswered.