Newer versions of the birth control pill carry a similar increased risk of breast cancer as earlier ones that were abandoned in the 1990s, a new study reveals.
Woman taking modern formulations of the pill have a 20% increased risk of breast cancer compared with those who’ve never been on hormonal contraception, the study of almost 2 million Danish women found.
“The risk increases with increasing duration of use and persists for more than five years, if used for longer than five years,” said study author Lina Morch, a senior epidemiologist with the University of Copenhagen in Denmark.
Still, experts cautioned that the absolute risk of breast cancer for any one women on the Pill remains very low.
Nevertheless, a similar amount of risk prompted the U.S. Food and Drug Administration to yank high-estrogen formulations of the pill off the market back in the early 1990s, said Mia Gaudet, strategic director of breast and gynecologic cancer research for the American Cancer Society.
“There had been some changes to oral contraceptive formulations in the ‘90s, and there was the hope those formulations would result in a lower risk of breast cancer,” said Gaudet, who was not part of the study. “We see from this data that is not the case.”
The first wave of birth control pills contained doses as high as 150 mg of estrogen. As research began to link estrogen to breast cancer, the FDA took off the market any formulations that had more than 50 mg of estrogen, Gaudet said.
Today, most versions of the pill contain between 15 and 35 mg of estrogen, Gaudet said. They also contain progestin, a synthetic form of the female hormone progesterone, which helps regulate the monthly menstrual cycle.
The new study was published Dec. 7 in the New England Journal of Medicine.
The relative dose of estrogen (or progesterone) is not the most important factor in the relationship between hormone therapy and breast cancer. The use of synthetic hormones rather than natural hormones is the biggest driving factor toward breast cancer.
However, so-called bioidentical hormone therapy also carries an increased risk of breast cancer. This is because any hormone therapy down regulates hormone receptors in the cells within two months of use. Downregulation requires a higher dosage to achieve the same effect. I believe that this downregulation is also associated with the increased risk of reproductive cancers in both men and women.
The Bottom Line:
All hormone therapy has some associated risk, including an increased risk of cancer. Always weight the relative risks verses the relative benefits when considering hormone therapy. If possible, please avoid it whenever possible.
Source: December 6, 2017 National Institutes of Health