Geriatric Assessment and Candidate Circulating Biomarkers of Frailty in Older Adults with Prostate, Bladder, and Kidney Cancer: A Narrative Review

Background and Objectives: Prostate, bladder and kidney cancers are frequently diagnosed in older adults, in whom chronological age and performance status poorly reflect functional reserve. Geriatric assessment (GA) identifies clinical vulnerability, whereas the contribution of candidate circulating biomarkers of frailty to risk stratification remains unclear. This narrative review summarizes the evidence on geriatric screening and assessment in older patients with urological cancers and on candidate circulating biomarkers associated with frailty, and it asks whether these add information beyond GA. Materials and Methods: Non-systematic literature searches of PubMed/MEDLINE, Embase, Web of Science and the Cochrane Library, last conducted on 1 October 2026, informed the narrative synthesis of English-language guidelines, reviews and clinical studies, focusing on adults aged 65 years or older. Exact search strings and screening counts were not retained. Results: In cohorts of mixed tumor types, the Geriatric-8 (G8) detected impairments on GA with about 82–85% sensitivity and 63–65% specificity, and an abnormal score was associated with shorter survival and more postoperative complications, including in urological cohorts. Frailty is independently associated with adverse outcomes after radical cystectomy and in renal cell carcinoma, and androgen deprivation is associated with loss of lean mass. C-reactive protein and interleukin-6 are the biomarkers most consistently associated with frailty in cross-sectional studies, but longitudinal confirmation is limited; evidence for haptoglobin and transferrin is sparse. All markers with adequate data, including the neutrophil-to-lymphocyte ratio, albumin, fibrinogen and growth differentiation factor-15, also relate to tumor stage or prognosis and are therefore non-specific. Most biomarker–frailty data come from populations without urological cancer. In a study of older patients with mixed cancer types, commonly available laboratory tests provided modest additional prognostic information beyond clinical variables and GA. Conclusions: The evidence reviewed does not establish a circulating biomarker panel validated to measure biological aging or to guide treatment intensity in older patients with urological cancers. We outline a conceptual framework in which biomarkers form an exploratory layer added to G8 screening and GA, and we identify the validation steps required before clinical use.