When would you feel comfortable with patients who have a history of hormone-receptor positive breast cancer using hormonal IUDs (e.g. Mirena)?  

While we typically recommend removing progesterone-secreting IUDs in patients with ER+ breast cancer, especially while receiving chemotherapy or adjuvant endocrine therapy, there is no data that I am aware of to support this recommendation, and we sometimes administer a systemic progestin ...

These discussions around Mirena IUD use and what is "safe" are complicated as the data has some limitations. Progesterone at physiologic levels appears to enhance breast cancer signaling and proliferation in estrogen sensitive cells exposed to estrogen. Antiproliferative effects of progestins like m...