PURPOSE: The intended clinical value of frailty screening is to identify unfit patients needing geriatric assessment (GA) and to prevent unnecessary GA in fit patients. These hypotheses rely on the sensitivity and specificity of screening tests, but they have not been verified. METHODS: We performed a cross-sectional analysis of outpatients age >/= 70 years with prostate, breast, colorectal, or lung cancer included in the ELCAPA cohort study (ClinicalTrials.gov identifier: NCT02884375) between February 2007 and December 2019. The diagnostic accuracy of the G8 Geriatric Screening Tool (G8) and modified G8 scores for identifying unfit patients was determined on the basis of GA results. We used decision curve analysis to calculate the benefit of frailty screening for detecting unfit patients and avoiding unnecessary GA in fit patients across different threshold probabilities. RESULTS: We included 1,648 patients (median age, 81 years), and 1,428 (87%) were unfit. The sensitivity and specificity were, respectively, 85% (95% CI, 84 to 87) and 59% (95% CI, 57 to 61) for G8, and 86% (95% CI, 84 to 87) and 60% (95% CI, 58 to 63) for the modified G8 score. For decision curve analysis, the net benefit (NB) for identifying unfit patients were 0.72 for G8, 0.72 for the modified G8, and 0.82 for GA at a threshold probability of 0.25. At a threshold probability of 0.33, the NBs were 0.71, 0.72, and 0.80, respectively. At a threshold probability of 0.5, the NBs were 0.68, 0.69, and 0.73, respectively. No screening tool reduced unnecessary GA in fit patients at predefined threshold probabilities. CONCLUSION: Although frailty screening tests showed good diagnostic accuracy, screening showed no clinical benefits over the GA-for-all strategy. NB approaches, in addition to diagnostic accuracy, are necessary to assess the clinical value of tests.