In this study, we prepared an immuno-PET imaging agent using desferoxamine (DFO)-pertuzumab labeled with 89Zr, performed the biodistribution and PET imaging in breast cancer xenograft models for monitoring therapeutic responses to HER2-targeted therapy, and evaluated the usefulness of 89Zr-DFO-pertuzumab for the treatment of HER2-targeted therapeutics, trastuzumab or HSP90 inhibitor, 17-dimethylamino- ethylamino-17-demethoxygeldanamycin (17-DMAG), in trastuzumab-resistant JIMT-1 breast cancer models. Here, ERBB2 is linked to breast cancer.