Women with hormone receptor-positive breast cancer are usually prescribed Tamoxifen or Raloxifene, pills that reduce the risk of cancer in high-risk patients, prevent cancer from returning as well as to fight a current cancer. Please read about the STAR study that compares these two medications' ability to fight cancer.
Besides the ovaries, estrogen comes from fat cells so overweight patients should lose some pounds in their effort to lower estrogen levels and fight the cancer. Statistically, overweight patients have a higher mortality rate.
In pre-menopausal women, the primary source of estrogen production is the ovaries and they are sometimes surgically removed or shut down with medication.
In post-menopausal women, a class of drugs called aromatase inhibitors (AI's) may be used instead of Tamoxifen. These inhibitors prevent androgen from turning into estrogen in the blood. Right now there are three that are FDA approved for fighting breast cancer: anastrazole (Arimidex), exemestane (Aromasin), and letrozole (Femara).