Are you planning to start running IHC HER2 testing on all tumor types, even those where HER2 overexpression is less typical, in light of tumor agnostic approval of trastuzumab deruxtecan?  

In my practice, I recommend HER2 IHC testing for all patients with advanced cancers, especially for those with epithelial cancers. For patients in whom HER2 positivity is rare, I also take into account any concerns about tissue availability as well as clinical eligibility for HER2-targeted therapy.

The recent tumor-agnostic approval of trastuzumab deruxtecan (T-DXd) has shifted the landscape of HER2 testing strategy. Historically, HER2 evaluation was confined to tumor types with precedent—breast, gastric, and later lung and colorectal cancers.The question now is how to incorporate HER2 t...