Background: This analysis evaluated HRQoL as exploratory endpoints in CheckMate 648, a randomized, open-label, global Phase 3 study, evaluating treatment with N+I, N+CT and CT alone in inoperable advanced, recurrent, or metastatic ESCC. Methods: The effects of N+I vs N+CT vs CT on HRQoL were assessed using the Functional Assessment of Cancer Therapy-Esophageal (FACT-E) (including the GP5 item to assess impact of side effects) and EQ-5D-3L. A mixed model for repeated measures was used to evaluate longitudinal changes from baseline (BL) and differences between treatment groups. Comparison of the risk of being bothered by the side effects of treatment was estimated for the GP5 using generalized estimating equation (GEE). Time to confirmed deterioration (TTCD) was assessed using Kaplan-Meier plots along with Cox proportional hazard models. Analyses were conducted on both the all-randomized population and the subset of patients with PD-L1 expression ≥1%. Results: 970 pts were randomized 1:1:1 to N+I (n=325), N+CT (n=321), or CT (n=324). 90% of pts completed both a BL and at least one on-treatment assessment and were included in the PRO analysis population. FACT-E (all randomized pts). Study showed similar BL scores across all 3 treatment groups. Changes from BL showed a trend towards better HRQoL for pts treated with N+I and N+CT compared to CT alone, however these results were not statistically significant. Patients treated with N+I had significantly decreased risk of experiencing bother associated with the side effects of treatment than patients treated with either N+CT or CT. TTCD analysis demonstrated delayed deterioration for pts treated with N+CT vs CT. Findings for PD-L1 ≥1% subpopulation were similar to all randomized pts. Conclusions: In pts with inoperable advanced, recurrent, or metastatic ESCC, HRQoL is maintained throughout treatment with N+I and N+CT. Trends towards better HRQoL and decreased risk of deterioration were observed with N+I and N+CT compared to CT alone. Clinical trial information: NCT03143153.