Tamoxifen fools the receptors into thinking it's estrogen, so cancer cells lock into the Tamoxifen instead.

Femara completely shuts down estrogen production. It's used for any estrogen-positive cancers. Some breast cancers are estrogen-positive and some are negative. For estroge-negative cancers there's another class of drugs called aromatase inhibitors, such as Irimidex.

One of the possible side effects of Femara is bone loss. I had a baseline bone density test in February and will repeat yearly. If there's significant loss I may start Fossamax. Another side effect -- not on the insert sheet, but my oncologist says it's not uncommon -- is worsening of existing arthritis conditions. Unfortunately, I have this and some days everything hurts, which it didn't before. I was thinking of starting a post in health. Maybe I'll go there now.