OBJECTIVES: This study evaluated health-related quality of life utility in previously untreated non-small cell lung cancer (NSCLC) patients. METHODS: This study examined the EQ-5D-3L data collected from patients enrolled in the KEYNOTE-024 trial, a multicenter, worldwide, randomized Phase III trial comparing pembrolizumab to standard-of-care platinum-based chemotherapy (SoC) in patients with previously untreated metastatic NSCLC with PD-L1 positive (Tumor Proportion Score [TPS]>=50%) tumors. Two approaches of defining health states are considered in analysing utility: time-to-death reflecting decline in cancer patient’s quality of life as they approach death, and progression-based health states. Generic health statuses assessed from the EQ-5D-3L questionnaire were converted to population-based utility values using published algorithms. The utility scores from the pooled treatment groups are reported. RESULTS: Data came from 283 patients who had at least one evaluable EQ-5D record. Mean utility score for patients in progression-free and progressive disease state is 0.78 (95% CI 0.77, 0.79) and 0.69 (95% CI 0.66, 0.72), respectively. Mean utility showed a decrease on disease progression of 0.09, which is considered as clinically meaningful. Patients were split into four groups based on their time to death after the EQ-5D questionnaire was taken - over 360 days, 180–360 days, 30–180 days, and under 30 days. Mean utility in each time-to-death category is 0.81(95% CI 0.77, 0.84), 0.73 (95% CI 0.68, 0.77), 0.63(95% CI 0.59, 0.67), and 0.54 (95% CI 0.43, 0.65). The results showed a large decrease in utility by time to death category. CONCLUSIONS: The results showed that quality of life for metastatic NSCLC patients rapidly deteriorates during the end of life period. Considerable deterioration of utility in NSCLC patients is associated with disease progression and time to death. The utility values estimated from the study will inform economic evaluations of treatments in previously untreated metastatic NSCLC.