Nivolumab in Nonsquamous Non–Small-Cell Lung Cancer

To the Editor: In the article on the CheckMate 057 trial, Borghaei et al. (Oct. 22 issue) 1 provide data on overall and progression-free survival among patients with advanced nonsquamous non–small-cell lung cancer who were receiving either nivolumab or docetaxel. In this trial, docetaxel initially appeared to have better outcomes than nivolumab, but the trends were reversed after 9 months (Fig. 1 of the article, available at NEJM.org). In such instances in which hazard functions for two treatment groups cross during the study follow-up, it is not clear how to interpret the observed hazard ratios of 0.73 for death and 0.92 . . .