Common IUD contraceptives may increase breast cancer risk, research suggests.
Women who used hormonal IUDs that slowly release the contraceptive levonorgestrel were 40 percent more likely to be diagnosed with the disease within at least five years than women who used other forms of contraception.
Among women who used them for more than ten years, the risk was up to 80 percent.
About one in five sexually active women in the US and one in six in Britain use IUDs, which are inserted into the uterus by a doctor and last three to eight years. Many women choose this so that they do not have to remember to take a pill every day.
The researchers noted that while the overall risk is low because IUDs are used long-term, “information about breast cancer risk should guide discussions about the benefits and risks.”
Researchers in Denmark found that using a hormonal IUD can increase the risk of breast cancer by 40 percent
The graph above shows how breast cancer rates have been increasing by one percent each year across all age groups, but slightly faster among women under 50
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Experts suggest this may be due to the influx of hormones such as estrogen and progesterone that bind to proteins in the breasts and fuel certain cancers.
They can also be riskier than pills or other forms of birth control because they are used for years, sometimes up to ten years.
A taste of the new research was published Monday in JAMA. However, the full investigation has not yet been released.
The team at the Danish Cancer Institute evaluated 157,190 girls and women aged 15 to 49 between 2000 and 2019. The average age of the participants was 38 years.
Half of the participants were prescribed a hormonal IUD using levonorgestrel, the same drug found in the morning-after pill, while the other half used other forms of contraception or did not use any contraceptive.
In the US, levonorgestrel is used in Kyleena, Liletta, Mirena, and Skyla IUDs.
Participants were also divided into groups based on how long they had been using the IUDs: zero to five years, five to 10 years, and 10 to 15 years.
The researchers found that hormonal IUDs led to an average 40 percent increased risk of breast cancer compared to other forms of contraception.
Those who used this form of contraception had an increased risk of 30 percent after zero to five years and of 40 percent over five to ten years.
The odds were highest for the long-term group, as women who used hormonal IUDs were 80 percent more likely to develop breast cancer after 10 to 15 years of use compared to women who used other contraceptives.
The team noted that the risk of taking birth control pills for breast cancer was about 20 percent.
The researchers did not explain why hormonal IUDs may increase the risk of breast cancer, although experts have suggested that the influx of hormones such as progesterone and estrogen may stimulate the growth of cancer cells in some types of breast cancer.
These hormone-sensitive cancers include estrogen receptor-positive (ER-positive) and progesterone receptor-positive (PR-positive) breast cancers, which contain proteins that bind to hormones and cause the growth of cancer cells.
Dr. Amy Berrington, professor of clinical cancer epidemiology at the Institute of Cancer Research in Britain, who was not involved in the study, said that while the findings appear bleak, “it is a small risk that should be taken into consideration along with the benefits of cancer. the contraceptive.
‘For younger women, the risk is probably even lower, because their risk of breast cancer is even lower.’
There were several limitations to the study. The study looked at correlation rather than causation, and full results have not yet been released.
It is also unclear which types of breast cancer were diagnosed in the women.
The findings come as breast cancer rates rise among American women under 50, which experts say could be due to changes in reproductive habits, such as women having children later or starting their periods earlier.
According to estimates from the American Cancer Society, about 310,000 women will be diagnosed with breast cancer this year, and about 42,000 will die.