Now, theres evidence thatprogestin-only contraceptivescarry a similarly increased risk.
The risk is even lower for younger women.
These hormones are also involved in the development of most breast cancers.
Francesco Carta fotografo / Getty Images
Comparatively, 39% of the cancer-free women received a hormonal contraceptive.
Thats a difference of 2030% in breast cancer risk, the researchers said.
In terms of actual breast cancer cases, the uptick isnt that drastic.
Women between ages 35 and 39 could see an additional 265 breast cancer cases per every 100,000 users.
Besides, young adults are more likely to take hormonal birth control than those in their 30s and 40s.
The long-term effects of progestin use are still unknown, Pirie said.
The researchers say its not yet clear how exactly progestin factors into increasing the risk of breast cancer.
Estrogen is aknown driverof breast cancer.
Far less is known about how progestin and progesterone factor in.
The role of progestin-only is unclear.
Many factors contribute to the development of breast cancer, including age, genetics, and some environmental exposures.
Hormonal contraception can reduce the risk of ovarian, endometrial, and colon cancers.
They may suggest that certain high-risk patients increase surveillance for cancer or seek genetic testing for risk factors.
2023;20(3):e1004188.
2020;41(2):320-344. doi:10.1210/endrev/bnz001
National Cancer Institute.Oral contraceptives and cancer risk.
