Aromatase inhibitors:

These drugs work by binding to the body’s aromastase enzyme, an enzyme responsible for producing estrogen. Many breast cancer cells depend on estrogen to grow and multiply quickly. Once the aromatase inhibitor has binded to the aromastase enzyme, estrogen cannot be produced by the enzyme. This lack of estrogen starves cancer cells, preventing them from growing and dividing. There are several aromatase inhibitors that are used to help treat advanced breast cancer including:

• Aromasin (generic name, exemestane)
• Femara (generic name, letrozole)
• Arimidex (generic name, anastrozole) 
• Megace (generic name, megestrol)

Recent studies suggest that some aromatase inhibitors may be more effective than tamoxifen in treating advanced breast cancer or may be useful after patients become resistant to tamoxifen. For example, Femara was recently FDA approved as an initial treatment option in advanced breast cancer patients after data showed that Femara may work better than tamoxifen in some patients (i.e., slows the growth of cancer and improves survival time). Recent studies also show that both Arimidex and Femara many be more effective than Megace for treating breast cancer.