How do you choose a neoadjuvant therapy regimen for a patient with a triple negative breast cancer and a synchronous ER-/Her2+ breast cancer?  

Assuming there is no contraindication to administration of an anthracycline, I would favor weekly paclitaxel and weekly carboplatin with every 3 week trastuzumab and pertuzumab x 12 weeks followed by ddAC x 4. This gives the TNBC the benefit of the higher pCR rate seen with the addition of carboplat...

In these cases I would treat the patient using AC-THP if her cardiac status would allow it. This would give you coverage for both the TNBC and HER2+ tumors. 

@William M. Sikov's approach is very reasonable and one that I have attempted myself especially when the triple negative component is node positive. The same discussion applies with weakly or heterogeneously positive her2 fish and the patient has node positive disease.  However there are some ...