How would you approach a patient with metastatic ER+/Her2+ who has progressed on trastuzumab/pertuzumab + tamoxifen after being in remission for 4yrs?  

There are several options for this patient, including 1) continuing Herceptin/Pertuzumab and change tamoxifen to a different hormonal therapy agent, 2) continuing Herceptin/Pertuzumab and switching hormonal therapy to a taxane, 3) switching to T DM1, 4) clinical trials of targeted agents such as CDK...

I agree with both @Cynthia X. Ma and @Praveen Vikas. In addition, level of ER/PR and presence or absence of HER2 heterogeneity, specifically in the repeat biopsy, may further finesse your treatments. For example, if HER2 heterogeneity is present, then TDM1 may be less effective, and first 2 options ...