The guideline, originally issued in 2007, is being published in ASCO’s Journal of Clinical Oncology (JCO) and the CAP’s Archives of Pathology & Laboratory Medicine. The joint guideline was prepared by an ASCO/CAP Update Committee consisting of experts in breast cancer and cancer biomarkers.
Approximately 15% of all newly diagnosed breast cancers are HER2-positive, meaning that the tumors have extra copies of the HER2 gene and/or high levels of the HER2 protein, which controls breast cancer cell growth and spread. HER2-positive tumours usually grow faster compared to HER2-negative tumours.
The purpose of HER2 testing is to identify patients who could benefit from effective HER2-targeted therapies, such as trastuzumab (Herceptin), lapatinib (Tykerb), pertuzumab (Perjeta), and T-DM1 (Kadcyla). These treatments can substantially improve survival in patients with HER2-positive invasive breast cancer. It is therefore important to accurately determine the HER2 status to ensure that patients most likely to benefit are offered a HER2-targeted treatment. At the same time, those that are unlikely to benefit can avoid side effects and costs associated with those drugs.
ASCO and CAP have also developed clinical tools and resources for oncologists and pathologists that summarise the findings and recommendations.