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 CDK4/6 inhibitor regimens. The choice of therapy may depend on comorbidities, age, disease burden, presence or absence of visceral mets. If the patient has limited disease burden and without visceral mets, in light of the 4 year progression free survival, it may be reasonable to switch to a different hormonal therapy or participating in clinical trials of targeted agents. Otherwise chemotherapy options are reasonable. T DM1 may be preferred than the...

I agree with both @Dr. First Last and @Dr. First Last. 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 may be better. In that case, for high ER/PR, switching to hormonal agent would be best, for low ER/PR, switching to chemotherapy would be best (in both cases continuing pertuzumab and trastuzumab).