1.   Estrogen fuels the growth of tumor cells in those cancers that have the estrogen receptors.

2.   Members of each group had initially had cancers that were fueled by estrogen, making them sensitive to the estrogen-blocking effects of tamoxifen.

3.   Previous research indicated that smoking may actually protect against breast cancer, because some breast cancers are fueled by estrogen, and smoking can decrease estrogen production.

4.   The drug works on breast cancers whose growth is fueled by estrogen, preventing the hormone from reaching them.

5.   Estrogen fuels the growth of about half of all breast cancers, especially those in older women.

6.   Estrogen fuels the growth of more than half of all breast cancers, especially those in older women.

7.   Some cancers are fueled by estrogen, the female sex hormone, and tamoxifen interferes with this.