A:Gefitinib 250mg Qd B:Gefitinib 250mg Qd combined with doublet chemotherapy: Pemetrexed (500mg/m²day 1 intravenously) plus carboplatin (AUC=5,day 1,intravenously) every 21 days, Gemcitabine (1000 mg/m² days 1, day8, intravenously) plus carboplatin (AUC=5,day 1,intravenously) every 21 days C:Gefitinib 250mg Qd combined with bevacizumab 7.5mg/kg intravenously per 21 days.