Progestins Increase Risk of Breast Cancer Metastasis

Previous studies have shown that women who take estrogen and progestin-containing hormone replacement therapies after menopause have an increased risk of developing breast cancer. Now, researchers at the University of Missouri have found that progestin-containing hormone replacement therapies increase the risk of breast cancer spreading to the lymph nodes. Professor Salman Hyder and colleagues compared the effect of several commonly used progestins on breast cancer tumors in animals. Results showed that progestins increase the number of blood vessels that are responsible for transporting existing cancer cells, which increases the chance that a cancer cell will metastasize. "Especially if there's a family history of breast cancer, it's advisable not to take progestins," said Professor Hyder. "The next step for this research is finding a type of progestin that does not cause tumor progression but still protects the uterus."