EGFR and squamous cell carcinoma: Herein, we have investigated the efficacy of two-step pretargeting strategy based on IEDDA reaction for tracing two clinically relevant antibodies, cetuximab and trastuzumab, with [18F]TAF (Fig. 1) in epidermal growth factor receptor (EGFR)-positive (A431 epidermoid carcinoma) and HER2-positive (BT-474 ductal carcinoma) xenografts in vivo.