4526Background: CheckMate 275 (NCT02387996), a phase II, single-arm study of nivolumab (3 mg/kg every 2 weeks) treatment in platinum-refractory patients (pts) with metastatic urothelial carcinoma, showed an objective response rate of 19.6% (95% CI, 15.0%–24.9%) with manageable toxicity. The objective of this analysis was to examine the impact of nivolumab on health-related quality of life (HRQoL) in the study. Methods: HRQoL was measured using the European Organization for Research and Treatment of Cancer Quality of Life Questionnaire (EORTC QLQ-C30) and three-level EQ-5D (EQ-5D-3L) and visual analog scale (VAS). Questionnaires were completed at baseline and every 8 weeks thereafter for the first 48 weeks. The analysis cohort included pts with scores recorded at baseline and ≥1 postbaseline assessments while on treatment. Data were analyzed using mixed models, adjusting for baseline score. Results: Of the 270 patients treated with nivolumab, 168 (62%) had an assessment at baseline and ≥1 postbaseline asse...