HER2 is a member of the Epidermal Growth Factor Receptor family, and amplification of HER2 or ERBB2 is seen in 8% of rectal cancer and 3% of colon cancer. HER2 and ERBB2 are different names for the same gene/ protein.

What is an amplification?

In simple terms, an amplification is when instead of the normal copy number of the gene in a cell, there are multiple copies of the gene. This results in “over-expression” of the protein. What this means is that a LOT of this protein gets made in the cell. If it’s a growth factor receptor like HER2 or ERBB2, that means this can cause a lot of growth factor signaling within the cell, which can lead to unregulated growth as seen with cancer.

HER2/ERBB2 amplification is not the same as a HER2/ERBB2 mutation.

How is HER2/ERBB2 amplification detected?

There are many ways to find out if your tumor has a HER2 or ERBB2 amplification including panel testing of the tumor and IHC.

HER2 or ERBB2 amplification can be “acquired” as a resistance mechanism, so good to test for it after progression on EGFR inhibitors like Vectibix or Erbitux.

Why is knowing the HER2/ERBB2 status of your tumor important?

For MSS CRC patients with tumors that are amplified for HER2 or ERBB2, there are 1st line clinical trials. There are effective targeted therapies with a much different side-effect profile for this subset of patients. So it’s important for people to know if their tumor is HER2/ERBB2 amplified. With higher rates seen in rectal cancer, this finding can make you eligible for additional effective treatments, so make sure to ask your care team about it.

Where can I learn more?

For those of you who are interested to learn more, this is a great DocTalk! to watch!