In metastatic breast cancer patients, who all had HER2 positive disease on biopsy, the combination of early metabolic response on FDG-PET (significant reduction in FDG uptake in >50% of the tumour load) and positive 89Zr-trastuzumab uptake (>50% of the tumour load) on the HER2-PET could predict treatment response to the antibody-drug conjugate (ADC) trastuzumab-emtansine (T-DM1) (Fig. 1A) 86. The gene discussed is ERBB2; the disease is neoplasm.