Impact of Levonorgestrel-Releasing Intrauterine Devices on Magnetic Resonance Imaging of the Breast

INTRODUCTION: Levonorgestrel-releasing intrauterine devices (LNG-IUD) are well established as both contraceptives and for the treatment of hypermenorrhoea. While progestogenic effects are mainly localised in the uterine cavity, levonorgestrel also confers a systemic influence, including on breast tissue. Current research suggests that there is an increase in background parenchymal enhancement (BPE) in magnetic resonance imaging (MRI) for patients with an LNG-IUD. METHODS: This retrospective study analyses MRIs of premenopausal women. Patients using an LNG-IUD (n = 30) were matched with 2 control patients without an LNG-IUD, based on age. MRI reports were evaluated for BI-RADS classification, non-mass enhancement, fibroglandular tissue, BPE, and the presence of foci. In addition, two experienced radiologists independently assessed the MRI scans (n = 90) in a blinded setting, evaluating BPE and diagnostic confidence. RESULTS: The results from the blinded evaluation by the radiologists showed a significant difference for BPE and interpretability between the two groups (p = 0.002 and 0.003, respectively). The odds of higher BPE for subjects with an IUD were 3.9 (95% CI: 1.69-9.37) compared to the control group. The odds of lower image interpretability for the IUD group were 3.48 (95% CI: 1.54-8.14) relative to the control group. CONCLUSION: The increased BPE in breast MRIs due to the use of an LNG-IUD potentially leads to limited diagnostic confidence. Women should be appropriately counselled regarding their contraceptive choices, given that MRI is often the preferred imaging modality for women with a high risk for developing breast cancer.