Could HER2 Heterogeneity Open New Therapeutic Options in Patients with HER2-Primary Breast Cancer

The purpose of this study is to determine if targeted imaging with a HER2-targeting PET tracer can detect HER2-positive metastases inpatients with HER2-negative primary breast cancer. Twenty-three patients have been accrued to the trial. Nine patients demonstrated suspicious foci on 89Zr-trastuzumab PETCT. Two of nine patients with suspicious foci had biopsy-proven HER2-positive metastases. Thus, 89Zr-trastuzumab PETCT may detect HER2-positive metastases in patients with presumed HER2-negtive primary breast cancer. This is an initial proof-of-concept that targeted imaging may help identify patients eligible for targeted therapies. However, false-positive results limit the ability of 89Zr-trastuzumab to be translated into clinical use, and a more specific radiotracer will be needed.