Cancer Risk Profile of the Levonorgestrel-Releasing Intrauterine Device: A Narrative Review.

Background/Objectives: The levonorgestrel-releasing intrauterine device (LNG-IUD) is widely used as a long-acting reversible contraceptive and as a therapeutic option for heavy menstrual bleeding, endometriosis, adenomyosis, and endometrial hyperplasia. Although its predominant effect is local, systemic levonorgestrel exposure has raised questions regarding its potential influence on cancer risk. This review aims to summarise and critically appraise the available evidence on the association between LNG-IUD use and gynaecologic, breast, and selected non-gynaecologic malignancies (including colorectal, lung, pancreatic, gastric, thyroid, skin [melanoma], and haematological cancers). Methods: A structured narrative review was developed by a multidisciplinary expert group affiliated with the European Society of Gynaecological Oncology (ESGO) and the European Society for Gynaecological Endoscopy (ESGE). PubMed/MEDLINE, Embase, and Scopus were searched in December 2024 without publication-date restrictions. We critically appraised epidemiological and clinical evidence on LNG-IUD use and breast, endometrial, ovarian, cervical, and selected non-gynaecologic cancer risks, prioritising population-based cohorts, registry-based studies, case-control studies, systematic reviews, and meta-analyses. Results: The strongest and most consistent evidence supports a substantial reduction in endometrial cancer risk among LNG-IUD users, with a possible protective association also suggested for ovarian cancer. Available data do not indicate a clear increase in cervical cancer, CIN3+, or invasive cervical disease. In contrast, evidence for breast cancer remains heterogeneous, with some registry-based studies suggesting a modest relative increase and other cohort or case-control studies showing no significant association. Evidence regarding non-gynaecologic cancers remains limited and inconclusive. Conclusions: Overall, current evidence suggests that the LNG-IUD has a favourable oncological safety profile, with the strongest evidence supporting a significant reduction in endometrial cancer risk and a potential protective effect against ovarian cancer. There is no evidence pointing to increased risk of cervical cancer. However, results related to breast cancer are mixed, and a slight risk increase cannot be ruled out; thus, counselling should be personalised based on the indication, menopausal status, duration of use, and individual breast cancer risk.