That might explain why using combined progestin and estrogen therapy results in a lower risk of endometrial cancer than use of unopposed estrogen therapy. The study authors concluded that the benefits of estrogen alone outweigh its risks. For each case of breast cancer in women due to long-term estrogen use, more than six deaths from heart disease are prevented, they write. In the United States, recent population statistics show that 110 of every 100,000 women develop breast cancer annually. This is five times greater than the rate of endometrial cancer, which is 21 cases in every 100,000 women.
Women also are more likely to die from breast cancer than from endometrial cancer.
Ross says the researchers hope to look into how breast cancer risk differs among women on hormone replacement therapy with different characteristics, such as family history of breast cancer, history of benign breast disease and exercise. They also hope to look at whether the increased risks from hormone replacement therapy are more likely to be in those expressing estrogen and progestin receptors. The authors concluded that doctors should provide women with information about the possible effects of hormone replacement therapy, and women should be told where uncertainty still remains in weighing risks against benefits.