Levonorgestrel-releasing and copper intrauterine devices and the risk of breast cancer

BackgroundThis study compares the risk of breast cancer for levonorgestrel-releasing intrauterine devices (LNGIUD) versus copper IUDs (CUIUD) in women younger than 50 years of age.Study DesignRetrospective, population-based, case-control study using cancer registers in Finland and Germany, powered to exclude a 1.5-fold risk of breast cancer.ResultsAnalysis of 5113 breast cancer cases diagnosed 2000–2007 and 20,452 controls — matched by year of birth and area of residence — yielded relative risk estimates approaching unity with 95% CI crossing 1.0 for all comparisons, including ever-use of LNGIUD versus CUIUD (adjusted OR, 0.99; 95% CI, 0.88–1.12) and current use at time of diagnosis (adjusted OR, 0.85; 95% CI, 0.52–1.39), as well as for sub-analyses by country, age, tumor characteristics and period, recency and duration of use prior to diagnosis.ConclusionThis study does not indicate an increased risk of breast cancer for users of LNGIUD. No indications for tumor promotion or tumor induction were found.