PURPOSE: The ISTANA (IRESSA as Second-line Therapy in Advanced NSCLC-KoreA) study compared gefitinib with docetaxel in patients with advanced or metastatic non-small cell lung carcinoma (NSCLC) pretreated with platinum-based chemotherapy. EXPERIMENTAL DESIGN: We conducted a multicenter, randomized, open-label phase III trial of gefitinib (250 mg/d) versus docetaxel (75 mg/m(2) day 1 every 3 weeks) in patients with advanced or metastatic NSCLC treated with one previous platinum-based chemotherapy. The primary endpoint was progression-free survival. RESULTS: A total of 161 patients (male, 62%; never smoker, 41%; adenocarcinoma, 68%) were enrolled. Progression-free survival was longer for gefitinib compared with docetaxel (hazard ratio, 0.729; 90% confidence interval, 0.533-0.998; one-sided P = 0.0441). Gefitinib significantly improved objective response rate (28.1% versus 7.6%; two-sided P = 0.0007). In the final analysis of overall survival, the hazard ratio was 0.870 (95% confidence interval, 0.613-1.236; two-sided P = 0.4370). No significant differences were seen in the quality of life or symptom improvement rates between the two treatment groups. Gefitinib was well tolerated, was consistent with previous data and disease, and had fewer serious adverse events and fewer Common Terminology Criteria for Adverse Events grade 3 or 4 adverse events than docetaxel. The incidence of interstitial lung disease-type events was 3.7% (n = 3) with gefitinib and 3.9% (n = 3) with docetaxel. CONCLUSIONS: The primary endpoint of progression-free survival was longer with gefitinib than docetaxel, and the secondary endpoints showed superior objective response rate, good tolerability, and similar quality of life improvement rates for gefitinib than docetaxel. Therefore, gefitinib is an important valid treatment option for second-line therapy for Korean NSCLC patients.