Women taking the pill or other hormonal contraception face a 20% higher risk of breast cancer than those not using this type of birth control, according to new research.
A new study carried out in Denmark suggests that the risk increases when this type of contraception is used for a longer timeframe and that the risk remains in place for about five years after women stop taking the hormones.
“The study confirms…a risk that was initially reported with the use of older, often higher-dose formulations also applies to contemporary formulations of oral contraceptives”
Professor David Hunter
It was already known that previous versions of the pill increased the risk of breast cancer.
This latest research shows that the risk of breast cancer has not been tackled by newer forms of hormonal contraception.
The study, published by the New England Journal of Medicine, looked at 1.8 million Danish women aged 15 to 49 and compared outcomes for those who had used hormonal contraceptives and those who had not.
It included looking at oral combination contraceptives that contain estrogen and progestin, and the progestin-only intrauterine system – also known as the hormonal coil.
The women were tracked for an average of 11 years, and a 20% higher risk of breast cancer was found in those who had used hormonal contraception, according to the paper, called Contemporary Hormonal Contraception and the Risk of Breast Cancer.
But researchers said the increased risk is still very small - just one extra case in every 1,500 women using hormonal contraception for more than five years.
”The risk of breast cancer was higher among women who currently or recently used contemporary hormonal contraceptives than among women who had never used hormonal contraceptives, and this risk increased with longer durations of use; however, absolute increases in risk were small,” said the research paper.
David Hunter, professor of epidemiology at the University of Oxford’s Nuffield Department of Population Health, commented on the findings, also in the New England Journal of Medicine.
“In the 1980s and 1990s, there was some optimism regarding… a formulation that would reduce a woman’s risk of breast cancer, but research…appears to have stalled”
Professor David Hunter
“The advantage of the analysis by Mørch et al. is that most of the [contraceptive] formulations used were those that have been prevalent in Denmark since 1995; the [previous] data were based on the use of formulations in the 1980s and earlier,” he said.
“The study by Mørch and colleagues confirms that the increased breast-cancer risk of approximately 20% among women who were currently using oral contraceptives - a risk that was initially reported with the use of older, often higher-dose formulations - also applies to contemporary formulations of oral contraceptives,” he added.
However, he also noted that the 20% higher risk of breast cancer should be understood in the context of low incidence rates of breast cancer among younger women.
“Most of the cases that occurred in this analysis occurred among women who were using oral contraceptives in their 40s,” said Professor Hunter.
He also said the study showed there was a need for more research to find better forms of oral contraceptives.
“In the 1980s and 1990s, there was some optimism regarding the development of a formulation that would reduce a woman’s risk of breast cancer, but research into this possibility appears to have stalled,” he said.