In the 1980s and 1990s, breast cancer rates steadily increased, in parallel with the rise in obesity and the use of hormone replacement therapy, which involves estrogen.

But many studies have already linked estrogen therapy with increased risk of breast cancer and death from the disease.

If possible, estrogen therapy should be discontinued at least 4 to 6 weeks before any surgery associated with an increased risk for thromboembolism or during periods of prolonged immobilization.