EGFR and lung cancer: More recently, the EGFR C797S mutation was identified in cell-free plasma DNA from subjects with advanced lung cancer whose tumors had developed resistance to AZD9291, proving that the C797S drug-resistance mutation is clinically relevant [21], and L718Q mutation was also identified in a 71-year old woman with advanced lung adenocarcinoma harboring the L858R mutation who became resistant to AZD9291 [22].