[Debbie L.]

Can the breast cancer mutate into a hormone driven one?

It happens, but rarely. More often, if it changes from the primary subtype when metastasis happens, it goes the other way (hormone positive to negative) but that is rare, too. Still, the changes (mutations or selection pressure changes) that can happen are considered important enough to biopsy the metastasis if possible, in order to make the best treatment choices when there's a recurrence. The other possible change is to the HER2 status, and I think that's more likely to be in the direction of negative to positive. Questions remain about when there are multiple sites of mets -- should all of them be biopsied, if possible (because each could be a different clone)?

The heterogeneity (mix of targets/subtypes) within tumors was a BIG topic at SABCS this year. Which leads me to a slightly OT ramble: If we're trying to use targeted therapy, and the tumors keep changing/mutating/becoming resistant, it's unknown if we could ever target enough targets to eradicate the cancer. Immunotherapy seems to care less about targets and escape mechanisms and holds the potential (not yet realized) to have a broader effect with fewer toxicities.

Maybe if you explain exactly what is your concern about this, we can try to answer your question better?

Debbie