When do you perform HER2 testing in patients with colorectal cancer?

HER2 amplification is seen in a small but distinct subset of colorectal cancer. This subset has 2 unique characteristics:

1. They are predominantly RAS wild type tumors.
2. They do not respond to anti-EGFR agents, i.e. HER2 amplification is a negative predictor of anti-EGFR antibody (cetuximab and panitu...