The risk of breast cancer declines in the years after a woman stops using hormonal contraceptives, according to a study published on Tuesday.
The research, published in the journal PLOS Medicine, found that women taking hormonal contraceptives have a 20 to 30 per cent higher risk of developing breast cancer than those who do not use them.
It also established that women who use hormonal contraceptives with both estrogen and progestogen have the same risk of developing breast cancer as those who use just progestogen.
The risk remains about the same regardless of the delivery method — oral pill, IUD, implant or injection — or whether it is a combined pill or progestogen alone.
The researchers who carried out the investigation stressed that the increased risk of breast cancer needs to be weighed against the benefits of hormonal contraceptives, including the protection they provide against other forms of female cancer.
Taking into account that the likelihood of breast cancer increases with age, the authors of the study calculated how much absolute excess risk is associated with hormonal contraceptives.
For women taking hormonal contraceptives for a period of five years between the ages of 16 to 20, it represented eight cases of breast cancer per 100,000, they said. Between 35 and 39 years old, it was 265 cases per 100,000.
“Nobody wants to hear that something that they’re taking is going to increase their risk of breast cancer by 25 per cent. What we’re talking about here is very small increase in absolute risk.
“These increases in risk for breast cancer have to, of course, be viewed in the context of what we know about the many benefits of taking hormonal contraceptives.
“Not just in terms of birth control, but also because we know that oral contraceptives actually provide quite substantial and long term protection from other female cancers, such as ovarian cancer and endometrial cancer,” said Gillian Reeves, a professor of statistical epidemiology at the University of Oxford and a co-author of the study.
The study also confirmed, like others, that the risk of breast cancer declines in the years after a woman stops using hormonal contraceptives.
Stephen Dufy, a professor at Queen Mary University of London who did not take part in the study, described the findings as “reassuring in that the effect is modest.”
The research involved data from nearly 10,000 women under the age of 50 who developed breast cancer between 1996 and 2017 in the United Kingdom, where the use of progestogen-only contraceptives is now as widespread as the combined method.
Reeves said there were several explanations for the growing use of progestogen-only contraceptives.
They are recommended for women who are breast-feeding, who may be at risk of cardiovascular problems or smokers above the age of 35.
“It might just be because women are taking hormonal contraceptives possibly into later years now, so they are naturally at higher risk of those other conditions for which risk is increased with combined contraceptives,” Reeves said.