Do you routinely add endocrine therapy to anti-HER2 maintenance therapy after 6 cycles of THP for metastatic ER+ HER2+ breast CA?  

Yes, if I am treating triple positive, I generally add ET to HP regardless of whether the patient received THP or not. The therapeutic window is wide, and likelihood of cross-talk interfering with long-term anti-HER2 effectiveness is high. While not tested systematically, HP alone is likely a r...