BACKGROUND: Phase 3 clinical data has shown higher proportions of patients with objective response, longer response duration, and longer overall survival with nivolumab versus docetaxel in patients with previously treated advanced non-small-cell lung cancer (NSCLC). We aimed to evaluate the long-term benefit of nivolumab and the effect of response and disease control on subsequent survival. METHODS: We pooled data from four clinical studies of nivolumab in patients with previously treated NSCLC (CheckMate 017, 057, 063, and 003) to evaluate survival outcomes. Trials of nivolumab in the second-line or later setting with at least 4 years follow-up were included. Comparisons of nivolumab versus docetaxel included all randomised patients from the phase 3 CheckMate 017 and 057 studies. We did landmark analyses by response status at 6 months to determine post-landmark survival outcomes. We excluded patients who did not have a radiographic tumour assessment at 6 months. Safety analyses included all patients who received at least one dose of nivolumab. FINDINGS: Across all four studies, 4-year overall survival with nivolumab was 14% (95% CI 11-17) for all patients (n=664), 19% (15-24) for those with at least 1% PD-L1 expression, and 11% (7-16) for those with less than 1% PD-L1 expression. In CheckMate 017 and 057, 4-year overall survival was 14% (95% CI 11-18) in patients treated with nivolumab, compared with 5% (3-7) in patients treated with docetaxel. Survival subsequent to response at 6 months on nivolumab or docetaxel was longer than after progressive disease at 6 months, with hazard ratios for overall survival of 0·18 (95% 0·12-0·27) for nivolumab and 0·43 (0·29-0·65) for docetaxel; for stable disease versus progressive disease, hazard ratios were 0·52 (0·37-0·71) for nivolumab and 0·80 (0·61-1·04) for docetaxel. Long-term data did not show any new safety signals. INTERPRETATION: Patients with advanced NSCLC treated with nivolumab achieved a greater duration of response compared with patients treated with docetaxel, which was associated with a long-term survival advantage. FUNDING: Bristol-Myers Squibb.