BACKGROUND: With the shift to immunotherapy (IO) in first-line (1L) treatment for patients with advanced non-small cell lung cancer (aNSCLC), this study aims to describe second-line (2L) treatment patterns and outcomes. METHODS: This retrospective study examined 2L outcomes in patients with stage IIIB-IV, epidermal growth factor receptor (EGFR)-/anaplastic lymphoma kinase (ALK) wild-type aNSCLC who started 1L therapy between 2016 and 2019 and received subsequent 2L therapy. Follow-up continued through November 2020. Subgroups included: 2L IO, 2L non-IO, and IO re-challenge (1L and 2L). RESULTS: A total of 194 patients initiated 2L therapy; 93 received IO (12 also in 1L), and 101 did not. For IO and non-IO, respectively: overall response rate (ORR) was 28.0% and 25.7%; median follow-up was 23.7 and 20.0 months; median realworld progression-free survival (rwPFS) was 8.4 and 5.1 months (p = 0.0006); median overall survival (OS) was 13.5 and 7.7 months (p = 0.0021). No deaths occurred in the IO re-challenge cohort after a median follow-up of 35.0 months. CONCLUSIONS: rwPFS and OS were consistent with clinical trials of 2L IO regimens. The few patients who received IO in 1L and 2L had favorable rwPFS and OS. Future research on sequential IO therapies in 1L and 2L aNSCLC is warranted.