This means estrogen acts as fuel for the tumors. So if estrogen can be blocked, the hope is that the tumors may stop growing. Most of the estrogen in young women is made in the ovaries. The conversion is carried out by aromatase, which is blocked by drugs like Femara. The current standard drug for breast cancer is tamoxifen.
Tamoxifen blocks the effects of estrogen in a different way.
Overall, Femara was well tolerated, with similar side effects as tamoxifen. The most common of these is a tendency toward forming blood clots. In the study, Femara had fewer of these problems than tamoxifen. In 1997, Femara was approved as a treatment to be used if tamoxifen failed. But if the panel's recommendations are followed, Femara could take the lead as the preferred first treatment.