Oral contraceptives and invasive adenocarcinomas and adenosquamous carcinomas of the uterine cervix. The World Health Organization Collaborative Study of Neoplasia and Steroid Contraceptives.

Data from a hospital-based case-control study collected between 1979 and 1988 in 10 participating hospitals in eight countries were analyzed to determine whether use of combined oral contraceptives alters the risks of invasive adenocarcinomas and adenosquamous carcinomas of the uterine cervix. Information on prior use of oral contraceptives, suspected risk factors for cervical cancer, and history of cytologic screening was ascertained from interviews with 271 women with adenocarcinomas, 106 with adenosquamous carcinomas, and a large pool of hospitalized controls, from which 2,887 were matched to the cases included in this report. History of smoking and anogenital warts and blood specimens for measurement of herpes simplex and cytomegalovirus antibodies were obtained from subsets of these women, as was a sexual history from a subset of their husbands. The epidemiologic features and associations with oral contraceptives were similar for adenocarcinoma and adenosquamous carcinoma. For both types combined, risk increased with duration of oral contraceptive use, was highest in recent and current users, and declined with time since cessation of use. These trends in risk were strongest for cancers that occurred in women under age 35 years, and the association with risk was somewhat stronger for high compared with low progestin potency products. The strength of the observed relation with oral contraceptives was about the same as has been observed for invasive squamous cell cervical carcinomas. Women who have used oral contraceptives should be considered at increased risk of adenomatous cervical carcinomas.