INVASIVE SQUAMOUS-CELL CERVICAL-CARCINOMA AND COMBINED ORAL-CONTRACEPTIVES - RESULTS FROM A MULTINATIONAL STUDY

Data from a hospital-based case-control study collected in 11 particip ating centers in 9 countries were analyzed to determine whether use of combined oral contraceptives alters risk of invasive squamous-cell ce rvical cancer. Information on prior use of oral contraceptives, screen ing for cervical cancer, and suspected risk factors for this disease w ere ascertained from interviews of 2361 cases and 13,644 controls. A h istory of smoking and anal and genital warts was obtained, and blood s pecimens were collected for measurement of antibodies against herpes s implex and cytomegalo viruses, from selected sub-sets of these women, as was a sexual history from interviews of husbands. The relative risk of invasive squamous-cell cervical carcinoma was estimated to be 1.31 , with a 95% confidence interval that excluded one, in women who ever used combined oral contraceptives. Risk of this disease increased sign ificantly with duration of use after 4 to 5 years from first exposure, and declined with the passage of time after cessation of use to that of non-users in about 8 years. No sources of bias or confounding were identified that offered plausible explanations for these findings. The strength of these results, and their consistency with those from othe r studies, suggest that a causal relationship may exist between use of combined oral contraceptives and squamous-cell cervical carcinoma. Wo men who have used these products for 4 or more years, and who most rec ently used them within the past 8 years, should receive high priority for cervical cytologic screening. (C) 1993 Wiley-Liss, Inc.