Is Milk Thistle safe for Estrogen/Hormone cancers?

Milk thistle is a phytoestrogen, which binds but doesn’t activate ER alpha.
ER alpha is a key player in mediating estrogen’s effects in cancer.
This is a good read about milk thistle and estrogen:
Milk Thistle kills MCF-7 cells.
MCF-7 cells = Estrogen positive breast cancer cells

https://www.sciencedirect.com/…/abs/pii/S0003986120304677

However we did come across a this mice study in which the MCF-7 cells grew.
Yes we know that’s a conflict. 
We do have a testimonial of someone using Milk Thistle ER+ breast cancer with a good outcome. 
Keep in mind that Milk Thistle not only protects the liver but it also blocks so many of cancer’s pathways.