EGFR and non-small cell lung carcinoma: Multivariate Cox regression analysis revealed ECOG score as an independent prognostic factor for PFS in stage IV NSCLC patients (Table 2), and the patients with EGFR 19del mutation had a longer PFS than those with exon 21 L855R mutation (13 vs. 9 months, P = 0.003) among the 64 EGFR-mutant NSCLC patients (Figure 1D–1F).