Study finds all hormonal contraceptives increase risk of breast cancer

A new study reveals that all types of hormonal contraceptives, including progestogen-only pills, have a slightly higher risk of breast cancer.

The researchers emphasise that the benefits of hormonal contraceptives, such as protection against other forms of female cancer, should be considered alongside the increased risk.

Earlier research established the risk of breast cancer with combined contraceptives that use both oestrogen and progestogen.

For over a decade, the usage of progestogen-only contraceptives has been increasing, but until recently, there had been limited research conducted on their association with breast cancer.

However, a study published in the journal PLOS Medicine has found that the risk of breast cancer for women using hormonal contraceptives containing both estrogen and progestogen is similar to those using only progestogen.

The study's authors have emphasised that the increased risk of breast cancer must be balanced against the benefits of hormonal contraceptives, which include protection against other forms of female cancer.

The new study has revealed that women who take hormonal contraceptives have a 20 to 30 per cent higher risk of developing breast cancer than those who do not use them. This is consistent with previous studies, including a large study from 1996.

The increased risk is independent of the type of contraceptive, whether it is a combined pill or progestogen-only, or the delivery method (oral pill, IUD, implant or injection).

The study authors factored in the correlation between age and breast cancer risk and determined the absolute excess risk associated with hormonal contraceptives.

They found that for women using these contraceptives for five years between the ages of 16 and 20, there would be eight additional cases of breast cancer per 100,000. For women aged 35 to 39, there would be 265 additional cases per 100,000.

Gillian Reeves, a co-author of the study and a professor of statistical epidemiology at the University of Oxford, acknowledged that people may be hesitant to hear that their contraceptive use can increase their breast cancer risk by 25 per cent.

However, she noted that the absolute increase in risk is very small. Reeves emphasised that the increased risk must be considered in light of the significant benefits of using hormonal contraceptives.

She said, "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."

The study also confirmed that the absolute excess risk associated with hormonal contraceptives is small, and the risk declines after discontinuation.

A study involving nearly 10,000 women under the age of 50 who developed breast cancer between 1996 and 2017 in the UK found that the risk of breast cancer associated with hormonal contraceptives was modest. Stephen Duffy, a professor at Queen Mary University of London who was not involved in the study, described the findings as "reassuring."

The study included data from a time period when the use of progestogen-only contraceptives had become as widespread as the combined method in the UK.

Reeves said that the growing use of progestogen-only contraceptives could be explained by several factors.

According to Reeves, progestogen-only contraceptives are often recommended for women who are breast-feeding, have a risk of cardiovascular problems, or are smokers over the age of 35.

The increase in their use could also be due to women taking hormonal contraceptives for a longer period. As a result, they may naturally be at a higher risk of the other conditions that are associated with combined contraceptives

(With inputs from AFP)