At the time of data cutoff on Nov 12, 2018, median follow-up for overall survival was 10·5 months (IQR 4·5-19·0) in the nivolumab group and 8·0 months (4·6-15·2) in the chemotherapy group. At a minimum follow-up time (ie, time from random assignment of the last patient to data cutoff) of 17·6 months, overall survival was significantly improved in the nivolumab group compared with the chemotherapy group (median 10·9 months, 95% CI 9·2-13·3 vs 8·4 months, 7·2-9·9; hazard ratio for death 0·77, 95% CI 0·62-0·96; p=0·019).