Background: NEJ009 study is the first randomized phase III trial that compared gefitinib plus chemotherapy with gefitinib in patients with untreated NSCLC harboring EGFR mutations. We report an updated OS and long-term tolerability analysis, including subgroup analyses focusing on a type of EGFR mutation and metastatic sites. Methods: Patients were randomly assigned to gefitinib (gefitinib 250 mg PO, QD) and GCP regimen (gefitinib 250 mg PO, QD combined with carboplatin AUC 5 and pemetrexed 500 mg/m2 in a 3-week cycle for up to six cycles, followed by concurrent gefitinib and pemetrexed maintenance). This study tested multiple primary endpoints, PFS, PFS2, and OS, which were analyzed using a preplanned hierarchical sequential testing method. Results: Three hundred forty-five patients were randomly assigned (gefitinib, n = 172; GCP, n =170). At latest data cut-off (May 22, 2020), although there was no significant difference in OS between the groups (HR, 0.82; 95% CI, 0.64 to 1.06; P=0.13), GCP still demonstrated significantly better PFS and PFS2 compared to G. The updated median PFS, PFS2, and OS was 11.2 months, 18.0 months, and 38.5 months in the gefitinib group and 20.9 months, 20.9 months, and 49.0 months in the GCP group, respectively. No severe adverse events occurred in the period since the first report. Conclusions: This updated analysis confirmed that the GCP regimen achieved significantly better PFS and PFS2 with an acceptable safety profile compared with gefitinib alone. The efficacy outcome of GCP is more favorable than gefitinib monotherapy as first-line treatment of NSCLC with EGFR mutation. Clinical trial information: UMIN000006340. Clinical trial information: UMIN000006340.