Despite the demonstrated efficacy of pembrolizumab in KEYNOTE-024, effectiveness and safety in routine practice remain unclear. The authors identified first-line pembrolizumab or chemotherapy patients from April 2013 to March 2021. The primary outcome was overall survival; the secondary safety outcomes included rates of hospitalization, emergency department visits, specialist visits, and adverse events. Baseline differences were adjusted using propensity score matching (1:1). The matched cohort included 2284 pairs. Median overall survival for pembrolizumab (13.0 months) was significantly longer than for chemotherapy (9.2 months), with a hazard ratio of 0.81 (95% CI: 0.71-0.92). Pembrolizumab patients reported significantly more adverse events and specialist visits, as well as a higher 1-year cumulative incidence of direct hospitalizations. The survival benefit of first-line pembrolizumab persists in the real world, although with increased toxicity and diminished benefit.