Ever-use of the intra-uterine device and the risk of ovarian cancer.

The association between the use of the intra-uterine device (IUD) and the risk of ovarian cancer is not well known. In this study, we sought to determine whether the use of an IUD is associated with a reduction in the risk of ovarian cancer. We searched Medline, EMBASE, Google Scholar, Scopus, ISI Web of Science and Cochrane database search, as well as PubMed (www.pubmed.gov) and RCT registry (www.clinicaltrials.gov) until the end of June 2019 to conduct a systematic review and meta-analysis comparing ever-use vs. never-use of an IUD and the risk of subsequent ovarian cancer. We obtained 431 records, of which 9 met inclusion criteria. A total of five case-control studies and four cohort studies were retrieved to establish the risk of ovarian cancer amongst ever-users of an IUD. Relative to the never-use of the IUD, ever-use conferred a lower risk of ovarian cancer with an estimated OR of 0.67 95% CI [0.60 - 0.74], p < .0001, I2 = 71%. This relationship remained significant when results were restricted to studies evaluating the levonorgestrel intrauterine system (LNG-IUD) alone, with an estimated OR of 0.58 95% CI [0.47 - 0.71], p < .0001, I2 = 0%, as well as when the analysis was stratified by study design, with an OR of 0.64 95% CI [0.56 - 0.74] for case-control studies, and OR of 0.71 95% CI [0.60 - 0.84] for cohort studies (p < .0001). Ever-use of an intrauterine contraceptive device reduces the risk of ovarian cancer by an average of 30%. Whether differences exist for duration of use, use of type-specific device, and specific tumour type needs to be addressed in future studies.Impact statementWhat is already known on this subject? The use of IUDs is very common practice in today's society. Its benefits regarding contraception, the treatment of abnormal uterine bleeding and even the reduction of the rates of endometrial cancer are well established. However, whether IUD's are associated with a reduction in the risk of ovarian cancer is unknown.What do the results of this study add? In this study, we show that the ever-use of the IUD reduces the risk of ovarian cancer by an average of 30%. We provide insight regarding the potential theories that may underlie these findings.What are the implications of these findings for clinical practice and/or further research? future studies will need to determine whether the beneficial effects found are a function of duration of use, of type-specific device, or specific tumour types. In the meantime, these findings may serve clinicians to reassure and counsel patients about the added benefits of intra-uterine devices.