Utilization of HER2 genetic testing in a multi-institutional observational study

Human epidermal growth factor receptor 2 (HER2) expression is amplified in about 20% of breast cancer tumors, and evaluation of HER2 status should influence therapy selection. A critical gap in our knowledge is the real-world implementation of HER2 testing and its impact on treatment decisions for women diagnosed with breast cancer. Objective Study aims were to assess use of HER2 testing, to describe characteristics of patients who do or do not receive HER2 testing, to describe which HER2 tests were used (fluorescence in situ hybridization [FISH] or immunohistochemistry [IHC]), and to evaluate trastuzumab use as a function of HER2 results.