New study connects long-term use of estrogen therapy to higher breast cancer risk

A new study has linked the long-term use of both estrogen plus progesterone and estrogen-only hormone therapy (HT) with a higher risk for developing breast cancer. “It’s already been confirmed that patients shouldn’t be undergoing estrogen plus progesterone hormone therapy for the long term,” said Wendy Y. Chen, who worked on the study. “What we found is that people should also be careful about longer-term use of estrogen-alone HT.” Chen presented the findings at the American Association for Cancer Research Annual Meeting. Chen’s team found that the risk for breast cancer was 88 percent higher in women who had taken estrogen plus progesterone for 10 to 14.9 years compared to women who did not receive HT, the risk increased more than twofold for women who used it for 15 to 19.9 years. For women who used estrogen-only HT, researchers found a 22 percent increased breast cancer risk if used for 10 to 14.9 years and a 43 percent greater risk associated with 15 to 19.9 years of use.