When do you recommend incorporating HER2 testing into the diagnostic pathway for tumor types where HER2 overexpression is not commonly assessed?

I would recommend HER2 IHC testing at the time of advanced cancer diagnosis or at the next therapy change, whenever HER2-targeted therapy would be considered in the treatment course.

For histologies not routinely assessed for HER2, I do not recommend universal upfront IHC at diagnosis. A pragmatic approach is reflex IHC at the time of advanced progression, when therapeutic impact is highest. In select cases—aggressive biology or early relapse after perioperative therapy—earlier ...

I agree with this approach. I recommend testing tissue for HER2 IHC early on in the course of metastatic disease for patients with advanced urothelial cancer. I often even use archival samples from radical cystectomies which are fairly concordant. Based on recently published data in a large (>2000 p...