HER2 (also known as ERBB2), human epidermal growth factor receptor-2, is a gene that plays a role in the control of cell growth and cell survival.
Some cells may have an increased number of copies of the HER2 gene (overamplification) which can cause the cells to make too many HER2 receptors (overexpression). When these changes occur, they allow abnormal cell growth and survival.
HER2 is altered in 4.69% of bowel cancer patients with HER2 amplification present in 2.22% of all bowel cancer patients.
If you do not have a mutation (also known as ‘wild-type’) in KRAS, NRAS or BRAF, you are more likely to have HER2 amplification.
If you have metastatic bowel cancer, you should be tested for HER2. However, HER2 testing is not recommended if your cancer already has an identified KRAS, NRAS, or BRAF mutation.
While HER2 biomarker testing is available in Australia, it is not currently indicated for metastatic bowel cancer and therefore not subsidised by Medicare. It can however be accessed privately.
For more information on HER2, visit: knowyourbiomarker.org/biomarkers/her2
Bowel cancer that has HER2 amplification or overexpression can be treated with targeted therapy using HER2 inhibitor drugs.
The combination of tucatinib (Tukysa) and trastuzumab (Herzuma) has been granted accelerated FDA approval in the US for RAS wild-type (no mutation) HER2-positive unresectable or metastatic bowel cancer that has progressed following chemotherapy.
In Australia, Herzuma is TGA-approved and ARTG registered, as a biosimilar brand of Herceptin, and is currently listed as a subsidised treatment for metastatic HER2-positive breast cancer on the PBS. (Herceptin was removed from the PBS by the manufacturer because of local price reductions that made it unsustainable for Herceptin to remain on the PBS with other biosimilars in the market.)
Tukysa is TGA-approved and ARTG registered for the treatment of patients with advanced unresectable or metastatic HER2-positive breast cancer but is not currently listed as a subsidised treatment on the PBS.
The combination as approved by the FDA is not currently TGA-approved or listed as a subsidised treatment on the PBS for the treatment of patients with metastatic HER2-positive bowel cancer.
If you have a HER2-positive bowel cancer tumour, we want to hear of your lived experience in accessing biomarking testing and treatment options.
