EGFR and cancer: Additionally, clinical data in other cancer types has also indicated the existence of de novo and acquired resistance to gefitinib (Ranson et al, 2002; Schiller, 2002; Kelly and Averbuch, 2004) and interestingly, a clear link between EGFR levels and predicted response to EGFR-targeted agents including gefitinib has not been observed (Arteaga, 2002; Ranson et al, 2002; Saltz et al, 2004).