LNG-IUS and Breast Cancer Risk

Growing numbers of women are using the levonorgestrel-releasing intrauterine system (LNG-IUS), whether for contraception or management of heavy menstrual bleeding. In a nationwide cohort study in Finland, researchers identified some 94,000 women aged 30 to 49 who had used the LNG-IUS for heavy menstrual bleeding from 1994 to 2007. From the Finnish Cancer Registry, the authors also identified breast cancers diagnosed before age 55 and by the end of 2012.

In >1 million woman-years of follow-up, <2 women per 1000 woman years of LNG-IUS use received diagnoses of breast cancer. In unadjusted analyses, LNG-IUS users had slightly higher risk for ductal breast cancer (standardized incidence ratio, 1.20) and lobular breast cancer (SIR, 1.33) compared…