In summary, we have shown that xenografts established from HNSCC cells resistant to EGFR TKIs are more hypoxic, poorly perfused and more glycolytic than those sensitive to EGFR inhibitors, and that these differences can be visualized and quantified non-invasively in vivo using functional MRI and PET imaging. The gene discussed is EGFR; the disease is head and neck squamous cell carcinoma.