In vivo study of erlotinib’s effect in nude mice carrying EGFR-mutant xenografts derived from NSCLC cell lines HCC827, PC9, and H1975 showed that high-dose treatment improved the progression-free survival of animals in two EGFR-mutant xenografts derived from HCC827 and PC9 cell lines, both carrying activating exon 19 deletion of EGFR. The gene discussed is EGFR; the disease is non-small cell lung carcinoma.