Jareid M, et al. - A levonorgestrel-releasing intrauterine system (LNG-IUS) may prevent ovarian cancer, but with a concurrent increased risk of breast cancer. In this population-based prospective cohort study, adjusted risks of ovarian, endometrial, and breast cancer were compared among ever- and never-users of LNG-IUS. A strongly reduced risk of ovarian and endometrial cancer, with no increased risk of breast cancer, was noted in ever-users of LNG-IUS versus never-users.