For example, epidermal growth factor receptor (EGFR) mutations present in ∼10% of the Western lung cancer population were retrospectively associated with maximal benefit from EGFR inhibitor drugs, after these drugs were initially licensed on the basis of minor benefit in unselected NSCLC populations (Shepherd et al, 2005; Pao and Chmielecki, 2010). This evidence concerns the gene EGFR and lung cancer.