Taking any type of hormonal contraceptive may increase a woman’s risk of breast cancer, a new study finds.
Using progestin-only hormonal contraceptives, including oral “mini-pills,” implants, injections and IUDs, increases the risk by 20% to 30%, scientists say.
Earlier research found that taking combined birth control pills containing estrogen and progestin, commonly known as the pill, was associated with a slightly higher risk of breast cancer, but the risk decreased after stopping the pill.
But experts say the benefits of taking birth control pills, such as protection against endometrial and ovarian cancer, may outweigh the risks of taking them.
The use of progestin-only contraceptives has increased substantially over the past few years, but to date there is limited information on their association with breast cancer risk.
In 2020, almost as many progestin-only oral contraceptives were prescribed as combined contraceptives in the UK.
According to the data, the absolute excess risk of breast cancer for women who used oral contraceptives for five years over a 15-year period ranged from 8 in 100,000 for women aged 16 to 20 who used it, to 8 in 100,000 for women aged 35 to 39 who used it 265 of them used the new discovery.
The data, collected by the Clinical Practice Research Datalink (CPRD), analyzed 9,498 women between the ages of 20 and 49 with invasive breast cancer and 18,171 similar women without breast cancer.
The experts said 44 percent of the women with breast cancer and 39 percent of the women without breast cancer who participated in the study had a prescription for hormonal contraceptives for an average of three years before their diagnosis.
About half of these women ended up taking progestin-only birth control pills.
The researchers combined the CPRD’s results on oral contraceptive use with those of other previously published studies to estimate absolute excess risk.
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Lead author Kirstin Pirie, from the Center for Population Health at the University of Oxford, said: “Given that a person’s underlying risk of breast cancer increases with age, the absolute excess risk of breast cancer associated with either oral contraceptive would be much larger. Small for women who use it at a young age.
“However, these additional risks must be seen in the context of the recognized benefits of contraceptive use in women of reproductive age.”
“I don’t really see any indication here that women need to change what they’re doing,” said Gillian Reeves, professor of statistical epidemiology and director of the Cancer Epidemiology Unit at the University of Oxford.
Combined oral contraceptives and progestogen-only birth control pills “are the same in terms of breast cancer risk, and they seem to have very similar effects” to other birth control pills, she said.
“I suspect that if women have been prepared to accept these risks in the past in exchange for the many benefits of taking hormonal contraceptives, they are likely to be prepared to continue doing so.”
“Rare breast cancer in young women”
Dr Kotryna Temcinaite, from the charity Breast Cancer Now, said: “For both types of birth control pills, if you stop using them, this increased risk of breast cancer decreases over time.
“Breast cancer is rare in young women. The slight increase in risk during women’s use of hormonal contraceptives meant that only a few additional cases were diagnosed.”