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Oral contraceptive and IUD use and endometrial cancer: A population‐based case–control study in Shanghai, China

Oral contraceptive (OC) and intrauterine device (IUD) use have been shown to be protective factors for endometrial cancer in several epidemiological studies; however, few studies have been conducted in Chinese populations. We evaluated the association between OC and IUD use and endometrial cancer risk in a population‐based case–control study among Chinese women in Shanghai, China. The study included 1,204 newly diagnosed endometrial cancer cases and 1,212 age frequency‐matched healthy controls. Logistic regression models were used to estimate adjusted odds ratios (OR) and their 95% confidence intervals (95% CI). In our study population, 18.5% cases and 24.9% controls reported having ever used OCs with an OR of 0.75 (95% CI, 0.60–0.93), after adjusting for known risk or protective factors for endometrial cancer. The risk of endometrial cancer decreased with long‐term use of OCs with the OR for more than 72 months of use being 0.50 (95% CI, 0.30–0.85). The effect of OC use remained 25 or more years after cessation of use; the associated OR was 0.57 (95% CI = 0.42–0.78) as compared to nonusers. Similarly, fewer cases than controls had ever used IUD, with the multivariable adjusted OR being 0.53 (95% CI = 0.43–0.65). A reduction in risk was observed regardless the duration of use or age at first and last use. These results suggest that OC and IUD use may confer long‐term protection against endometrial cancer. © 2006 Wiley‐Liss, Inc.