Contraceptive coil may be linked to increased risk of breast cancer, study shows

New research has raised concerns that women using a coil might face a slightly increased risk of breast cancer.

The study highlighted an "unexpected" link between the use of an intrauterine system (IUS), also known as a hormonal coil, and a higher incidence of the disease in women aged 15 to 49. It was found that there were 14 additional cases of breast for every 10,000 women who used a levonorgestrel-releasing intrauterine system (LNG-IUS) over five years, compared to those not on the contraceptive.

This comes despite previous beliefs that the coil would not elevate risk due to lower hormone exposure levels. Dr Lina Morch, team leader at the Danish Cancer Society’s Research Centre and who led the new study, said the risk identified needs to be taken “seriously”.

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She added: “For some, a hormonal IUD may still be the best choice. However, if a woman is approaching her 30s and 40s, when the risk of breast cancer is no longer minimal, it may make sense to consider other contraceptive options, such as a copper IUD.”

Dr Channa Jayasena, a reproductive endocrinology expert at Imperial College London, noted: "The levonorgestrel-releasing intrauterine systems (LNG-IUS) is a highly effective form of contraceptive for women."

“It is well known that prolonged use of the contraceptive pill slightly increases breast cancer risk. However, we have always assumed that the LNG-IUS would not increase breast cancer risk due to the much lower levels of hormone exposure to the whole body. The results of this study are therefore highly unexpected.”

Dr Mangesh Thorat of Homerton University Hospital and Queen Mary University of London (QMUL) said: “Similar to the British study (Fitzpatrick and colleagues) published last year, this study shows a small increase in the risk of breast cancer associated with the use of such coils.

“The existing evidence suggests that the increase in the risk is similar to that with oral contraceptive use. It is worth noting that this association has been known for at least a few years and a broad consensus exists among the medical fraternity that the overall benefits of hormonal contraception outweigh the harms like such small increase in the risk of developing breast cancer.”

He added: “The risk increases with increasing age and it is reasonable for women near 40 years of age to have a discussion with their healthcare practitioner regarding non-hormonal modes of contraception.”

The study analyzed data from about 160,000 Danish women, pointing out that LNG-IUS is the favoured hormonal birth control method among premenopausal Danish women over 30.

The describes an IUS as a small, T-shaped plastic device that is inserted into the womb by a doctor or nurse to prevent by releasing the hormone progestogen. This is different from the copper coil, or IUD, which is hormone-free and uses copper to prevent pregnancy.

Dr Simon Vincent, director of research, services and influencing at Breast Cancer Now, said: "We know that hormonal contraception can very slightly increase a woman’s risk of developing breast cancer, and this study contributes to that existing evidence."

"However, the overall risk of developing the disease for women aged 49 and under remains small, regardless of whether or not they have the hormonal coil or take any other form of contraception, and for many women the benefits of using these contraceptives outweigh any risks."

Dr Vincent further advised that women concerned about breast cancer and contraception should consult their doctor or reach out to Breast Cancer Now through its confidential helpline at 0808 800 6000.