Hormonal contraceptive pills increase risk of breast cancer, study finds

Older women who take the pill for five years and more have a higher risk of the disease

Research published by Oxford University has found that taking hormonal contraception increased the risk of breast cancer by 25 per cent. PA

Women with a family history of breast cancer should not be prescribed progesterone-only contraceptive pills due to a possible increased risk of the disease, a leading cancer specialist has said.

Research published by Oxford University found that taking hormonal contraception increased the risk of breast cancer by 25 per cent.

However, the risk of developing breast cancer because of contraceptive pills remains small, the research paper said.

The number of extra breast cancer cases for every 100,000 women who took the pill for more than five years was eight for those aged 16 to 20 and 265 for those aged 35 to 39.

The researchers also said the increased risk of breast cancer should be weighed against the benefits of hormonal contraceptives, including the protection they provide against other forms of female cancer.

Scientists in the study evaluated the records of 9,498 women in the UK aged 20 to 49 diagnosed with breast cancer from 1996 to 2017, and compared their results with a control group of 18,171 closely matched women without a breast cancer diagnosis.

Women taking a combined contraceptive pill of oestrogen and progesterone were 23 per cent more at risk from breast cancer, while those taking a progesterone-only pill (POP) carried slightly higher risk, at 26 per cent.

The study found a progesterone releasing intra-utrine coil had the highest risk of breast cancer, at 32 per cent.

“The findings suggest that current or recent use of all types of progestogen-only contraceptives is associated with a slight increase in breast cancer risk, similar to that associated with the use of combined oral contraceptives,” said Kirstin Pirie, statistical programmer at Oxford Population Health, and one of the lead authors.

“Given that a person’s underlying risk of developing breast cancer increases with advancing age, the absolute excess risk of breast cancer associated with either type of oral contraceptive will be smaller in women who use it at younger ages.

“These excess risks must, however, be viewed in the context of the well-established benefits of contraceptive use in women's reproductive years.”

Data collected by the Clinical Practice Research Datalink found 44 per cent of women with breast cancer and 39 per cent of women without the disease had a prescription for a hormonal contraceptive an average of three years before diagnosis, around half of whom were last prescribed a progestogen-only contraceptive.

More focus on prevention

Leading oncologists in the UAE said potential risks revealed in the Oxford study appeared to be small in younger women and should not deter most from taking the pill due to its benefits.

“The underlying mechanisms by which POP use may increase breast cancer risk are not well understood,” said Professor Humaid Al Shamsi, president of Emirates Oncology Society and professor of oncology at University of Sharjah.

“It is important to note that the overall risk of breast cancer associated with POP use is still relatively low, as reported in this study.

“Also, the benefits of using these contraceptives - such as preventing unintended pregnancies - may outweigh the potential risks for many women.”

Dr Al Shamsi said progestins in contraceptive pills could promote the growth of breast cancer cells by increasing levels of oestrogen and insulin growth hormones that stimulate cell proliferation.

Progestins may also induce inflammation and oxidative stress, which are associated with cancer development, he said.

“To reduce the risk of cancer, a healthy lifestyle and ideal body weight may have a larger impact than the risk of POP,” said Dr Al Shamsi.

“Women concerned about their breast cancer risk should discuss their options, to balance the risk and benefit of each contraception method with a healthcare provider.

“There should be more focus on shorter use of POP while needed, rather than staying on it for an extended period of time.

“I will not recommend the use of POP to a patient with a personal history or family history of breast cancer.”