Some common hormonal contraceptives are linked to a slightly higher risk of breast cancer than others. This is shown by a new study from Uppsala University, in which researchers followed more than 2 million women and teenage girls in Sweden to identify how different hormonal contraceptives affect the risk of breast cancer. Their findings were published by Hadizadeh et al in JAMA Oncology.
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.
Key Findings
The new study was made possible by Sweden’s unique national registers, which contain information on all dispensed prescriptions and all cancer diagnoses. Over 2 million women aged 13 to 49 years were included and followed via national registers from 2006 to 2019 to identify the risks associated with different types of contraception. All participants had no history of breast cancer, ovarian cancer, cervical cancer, uterine cancer, bilateral oophorectomy, or infertility treatment.
The study showed 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,” said Åsa Johansson, PhD, research group leader at Uppsala University and SciLifeLab and the study’s senior author. “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.”
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 of breast cancer than desogestrel.
Without looking at the type of contraceptive used by the women in the study, hormonal contraceptive use was linked to a 24% 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 the contraceptive products were used. Long-term use (5–10 years) of desogestrel products was associated with almost 50% higher risk, while the corresponding use of levonorgestrel products resulted in less than 20% 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,” said Fatemeh Hadizadeh, MD, PhD, 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.”
Disclosure: For full disclosures of the study authors, visit jamanetwork.com.
