Breast cancer risk varies between different hormonal contraceptives

Hormonal contraceptives are among the most used medicines worldwide. They give women effective control over fertility and have been an important part of women’s health since their introduction in the 1960s. Despite their many beneficial effects, hormonal contraceptives are also associated with certain well-known risks, including a modest increase in breast cancer risk.

“Hormonal contraceptives are widely used and have many benefits beyond protecting against unwanted pregnancies and subsequent abortions: they lower the risk of ovarian and endometrial cancers, help manage menstrual pain, heavy bleeding, and acne, and give women greater authority over their reproductive health,” says Dr Fatemeh Hadizadeh, researcher in Åsa Johansson’s group and lead author of the study.

In Sweden, hundreds of thousands of women use hormonal contraceptives every year. Over time, new types and formulations have been developed – ranging from combined pills containing both oestrogen and progestin to progestin-only methods such as pills known as mini-pills, hormonal intrauterine coils, implants and injections.
Earlier research mostly focused on oral combined pills, which were the most common form in the past. However, today progestin-only methods are increasingly popular and it is therefore important to study their long-term health effects in detail. In addition, several different progestins are used in different contraceptives, with varying potency and potentially also different effects on cancer risk.

In the new Swedish study, researchers examined different types of hormonal contraceptives and their association with the risk of breast cancer. The study was made possible by Sweden’s unique national registers, which capture all dispensed prescriptions and all cancer diagnoses. This study included more than two million women aged 13–49 in 2006 and followed them up through national health registers until 2019 to identify the risk associated with using different types of hormonal contraceptives. The study shows that the risks associated with hormonal contraceptive vary by type of progestin in the product.

“Not all hormonal contraceptives have the same effect on breast cancer risk. Our results point to specific progestins – particularly desogestrel – being associated with a higher risk of breast cancer. Some others, such as depot medroxyprogesterone acetate injections, did not show an increase,” says the study’s senior author Professor Åsa Johansson.

In addition, both combined pills and intrauterine devices containing levonorgestrel, which are among the most commonly prescribed products in Sweden, were shown to confer a lower risk compared to desogestrel. Moreover, pills containing drospirenone combined with oestrogen, which are also commonly used in Sweden, did not show evidence of increased breast cancer risk. These may therefore be a safer option for women at higher baseline risk.

"Hormonal contraceptives are highly effective and provide important health benefits, and we are not advising women to stop using them. However, breast cancer is increasing among young women and we currently lack non-surgical prevention strategies. Until better tools are available, avoiding medications that increase risk – especially among women who are already at higher risk – could make a real difference. The results of our study provide clinicians and women with actionable information," says Hadizadeh.