getting her2+ER- bc to reexpress ER & consequences more complicated than thought

[Lani]

Aromatase is only one of several enzymes that makes estrogen in postmenopausal women--AIs only block this enzyme and not the rest.

Fulvestrant degrades the actual receptor so that even if estrogen is around there is nothing to respond to it.

The problem is that estrogen has multiple effects all over the body and once the ER is degraded by Fulvestrant it never comes back. That is fine in areas of the body where the cells are constantly being replaced ie, once fulvestrant is blocked the new cells will have ERs, but estrogen is very important in the brain--tell me about it! (even in males, Rich66!) and noone seems to know for sure if fulvestrant crosses the blood-brain barrier.

Lots still to find out and that isn't even including under what circumstances estrogen promotes bc growth and under what circumstances it inhibits it!