As people seem to be given different advice about Mirena by different doctors, it’s worth checking the guidance provided by the Royal College of Obstetricians and Gynaecologists (RCOG)
They say that the The UK Medical Eligibility criteria for contraceptive use assesses the use of Mirena (aka LNG-IUS) in women with a past history of breast cancer and no evidence of current disease for the last 5 years as category 3. Which means that theoretical or proven risks usually outweigh the advantages of using the method.
They do not appear to provide any advice on use of Mirena in breast cancer patients primarily for heavy menstrual bleeding rather than contraception.
They note that it is protective against endometrial hyperplasia, especially for tamoxifen users. They confirm that it can be considered if non-hormonal contraception is unacceptable, and state that it may be considered on an individual basis and in consultation with the patients’ breast surgeon.
Tamoxifen can be used as a fertility treatment which explains some doctors’ concern about pregnancy after breast cancer diagnosis. Sometimes it can alleviate heavy menstrual bleeding so an option for anyone considering Mirena for heavy bleeding rather than contraception, and taking Tamoxifen, could be to just take Tamoxifen and see whether it reduces bleeding as well as protecting against breast cancer and only consider Mirena if Tamoxifen doesn’t work on the bleeding.
In Hansard House of Commons written answers October 17th 2007, it is reported that Dawn Primarolo MP was questioned about Mirena. She advised that, as a precautionary measure, Mirena would be contraindicated in women with progesterone dependent cancers and said that product information for health professionals would be updated to reflect this advice.
The question I would ask to any doctor that recommends it for someone who’s had breast cancer is that, since RCOG says that theoretical and proven risks of its use usually outweigh the advantages, what makes that patient an exception to the rule and what is the clinical evidence to support that opinion? It seems to me, following the Hansard report, that no doctor should advocate Mirena for any woman diagnosed with progesterone dependent breast cancer unless he or she can produce clear evidence to demonstrate why the contraindication can safely be ignored. A good doctor will not mind answering questions like this because it helps patients make informed decisions.
As to whether Mirena increases the risk of breast cancer in the general population, Cancer Research’s website says that there is no evidence that Mirena causes hormone dependent cancers and cites a Finnish Study of 17,000 users to support this statement. It is possible to find more detail about this study by searching on the internet where you can find the study report and also a paper by BfArM, part of the German Ministry of Health. BfArM regards the study as flawed and also notes that it was funded by Schering who markets Mirena in Europe and that the study authors conclude that additional, larger studies with a different methodological approach are needed to either confirm or refute their findings.
Curiously Cancer Research UK mentions that the manufacturer of Mirena says that it should not be used after a diagnosis of cervical, uterine and liver cancer, but omits to mention that the manufacturer advises that it should not be used by those who have or have ever been diagnosed wih breast cancer.
At the start of Feb 08, I wrote to NICE (National Institute for Clinical Excellence) to ask them to select Mirena as a topic to produce guidance for use in people who had been diagnosed with breast cancer, on the basis that doctors seem to give conflicting advice to patients and that little seems to be known about the role played by progesterone in development of breast cancer. They are still considering whether to select it as a topic.