INTRAUTERINE CONTRACEPTION AND THE RISK OF ENDOMETRIAL CANCER

Despite the increasing world-wide popularity of contraceptive intra-ut erine devices (IUDs), their potential long-term effects on the risk of developing endometrial carcinoma have been poorly studied. This paper reports on the relationship between intra-uterine contraception and e ndometrial cancer by analyzing epidemiological data from a large, mult icenter, population-based, case-control study of epithelial endometria l cancer. Cases were 437 women, 20 to 54 years of age, with histologic ally confirmed epithelial endometrial cancer ascertained through 6 pop ulation-based cancer registries in the United States. Controls were 32 00 women selected at random from the populations of these areas. The a ge- and parity-adjusted odds ratio (OR) for the association between ev er having used intra-uterine contraception and endometrial cancer was 0.51 (95% confidence interval (CI) 0.3-0.8). Although the protective e ffect increased with duration of use, a dose-response relationship amo ng users was not statistically demonstrable. The association did not v ary significantly with age at first or last IUD use or with time elaps ed since first or last IUD use. Years of education significantly modif ied the effect of intra-uterine contraception. Thus, intra-uterine con traception appeared to be strongly protective for women with at least 13 years of education (OR = 0.29, 95% CI, 0. 15-0.6). It is proposed t hat intra-uterine contraception exerts its protective effect through l ocal structural and biochemical changes in the endometrium that may al ter endometrial sensitivity and response to circulating estrogen and p rogesterone. (C) 1993 Wiley-Liss, Inc.