In mice bearing HER2-positive human ovarian cancer and breast cancer xenografts, as measured by ratios of tumor to background, bone and liver and by tumor SUVmax measurements according to type of chelator, [89Zr]Zr-DFOSq–trastuzumab showed improved PET imaging and radiolabeling efficiency over DFO-NCS, thus warranting further investigation. This evidence concerns the gene ERBB2 and breast cancer.