Some hormonal contraceptives linked to higher risk of breast cancer

Some common hormonal contraceptives are linked to a slightly higher risk of breast cancer than others. This is shown by a new Swedish study from Uppsala University, in which researchers followed more than two million women and teenage girls in Sweden to identify how different hormonal contraceptives affect the risk of breast cancer.

In Sweden, hundreds of thousands of women use hormonal contraceptives every year. Over time, new products have been developed – from combined contraceptive pills containing both estrogen and progestin to progestin-only methods such as mini-pills, hormonal coils, implants and injections. Previous research has mainly focused on combined contraceptive pills, which used to be the most common option. Today, progestin-based alternatives are becoming increasingly popular, making it important to study their long-term health effects in detail. In addition, several different types of progestins are used in both combined and progestin-only contraceptives, with varying potency and potentially different effects on cancer risk.

Desogestrel linked to higher risk of breast cancer

In the new study, which is the largest of its kind, researchers examined different types of hormonal contraceptives and their association with breast cancer risk. The study is made possible by Sweden's unique national registers, which contain information on all dispensed prescriptions and all cancer diagnoses. Over two million women aged 13–49 were included and followed via national registers from 2006 to 2019 to identify the risks associated with different types of contraception. The study shows that the risks vary depending on the type of hormone contained in the product.

Not all hormonal contraceptives have the same effect on the risk of breast cancer. Our results indicate that some progestins – particularly desogestrel – are linked to a higher risk of breast cancer, while others, such as depot medroxyprogesterone acetate injections, showed no increase."

Professor Åsa Johansson, research group leader at Uppsala University and SciLifeLab and study's senior author

The study also showed that both combined contraceptive pills and hormonal intrauterine coils containing levonorgestrel, which are among the most commonly used products in Sweden, were associated with a lower risk than desogestrel.

Good to avoid medicines that increase risk

Without looking at the type of contraceptive used by the women in the study, hormonal contraceptive use was linked to a 24 per cent increased risk of breast cancer, which corresponds to approximately 1 extra cancer case per 7,800 users per year. Moreover, the risk increased the longer they were used. Long-term use (5–10 years) of desogestrel products was associated with almost 50 per cent higher risk, while the corresponding use of levonorgestrel products resulted in less than 20 per cent increased risk. Contraceptive pills containing drospirenone combined with estrogen, which are also common in Sweden, were not linked to an increased risk of breast cancer. These may therefore be a safer option for women with a higher baseline risk.

"Hormonal contraceptives are highly effective and provide important health benefits, and we do not encourage women to stop using them," says Fatemeh Hadizadeh, the study's lead author. "In addition to protecting against unwanted pregnancies, they reduce the risk of ovarian and endometrial cancer, relieve menstrual pain and heavy bleeding, help with acne, and give women greater control over their reproductive health. At the same time, breast cancer is the most common cancer among women and until better preventive treatments are available, avoiding drugs that increase the risk can make a big difference – especially for women who are already at higher risk. The results of our study provide doctors and women with useful information to act on."