Background: Nivo, a PD-1 antibody, received FDA approval based on superior overall survival in metastatic squamous (SQ) and non-squamous (NSQ) NSCLC patients who have progressed on or after platinum-based doublet chemotherapy. The purpose of this study was to assess the frequency and associated costs of grade 2–4 AEs in the CheckMate 017 (SQ) and CheckMate 057 (NSQ) phase III pivotal trials of nivo vs doc in stage IIIB/IV NSCLC. Methods: Patient-level data from these two trials were utilized to estimate the frequency of TRAEs requiring management in the nivo and doc arms, including serious and non-serious TRAEs. Minimum follow-up for AE reporting at database lock was 12 months. Grade 3–4 AE costs by event were identified from Healthcare Cost and Utilization Project (HCUP) data in 2010, which were adjusted to reflect 2012-equivalent US costs. Healthcare utilization associated with grade 2 AEs was based on clinical opinion and costs were based on HCUP or other sources as appropriate. Results: In both trials, more TRAEs were observed with doc than with nivo (Table), and the cost of managing TRAEs was 15.8 and 10.7 times higher in the doc arm vs the nivo arm for the CheckMate 017 and CheckMate 057 trials, respectively. Patients in the doc arm incurred an additional $6,585 and $5,422 per patient in managing AEs compared with patients in the nivo arm in the above two trials, respectively. The total estimated costs of managing TRAEs during these trials are presented in the Table. Conclusions: Large estimated differences in costs were observed in managing TRAEs, favoring nivo in the CheckMate 017 and CheckMate 057 pivotal trials. The reduction in costs for managing AEs with the use of nivo should be considered when assessing the value of nivo in this patient population. Clinical trial information: NCT01642004, NCT01673867