PURPOSE: Concurrent chemoradiotherapy (cCRT) is the standard treatment for locally advanced and unresectable non-small-cell lung cancer. Population is aging, and Geriatric assessment (GA) has demonstrated its paper to select fit patients for active treatment and vulnerable, frail patients for interventions and/or palliative care in many histologies. Its role in locally advanced, unresectable non-small-cell lung cancer has been less explored. METHODS: To assess the capability of GA to detect frail patients not suitable for active treatment, we developed this exploratory non-interventional prospective study. All patients ≥ 70 years diagnosed with stage locally advanced and unresectable non-small-cell lung cancer were invited to undergo geriatric assessment. Secondary aims were description of population, exploring GA as prognostic factor, determination of toxicity profile and look for a frailty biomarker. RESULTS: From June 2017 to June 2020, 51 patients were included, of whom 35% (n:18) were classified as frail. Frail patients had less overall survival and more grade 3-4 toxicity. Exploratory results for frailty phenotype are described in the text. CONCLUSIONS: With the results of our study, we confirm that GA can detect frail patients unsuitable for treatment, with a higher risk of toxicity and less overall survival. A trend toward blood-test results for phenotype frailty can be hypothesis generation.