Frailty in older adults with cancer: A systematic review of evidence in colorectal, lung, prostate, and hematological malignancies.

Frailty is a well-established concept in geriatric medicine, defined as a state of increased vulnerability resulting from a decline in reserve and function across multiple physiological systems. However, in oncologic research, the term "frailty" is inconsistently used, often encompassing multidimensional screening tools, prognostic indices, or even abbreviated substitutes for comprehensive geriatric assessment (CGA). This heterogeneity hampers clinical applicability and comparisons across studies. The aim was to systematically review the prevalence, tools used, and clinical impact of frailty in older adults with cancer across four tumor types: lung, colorectal, prostate, and hematologic malignancies. We conducted a systematic review following the PRISMA guidelines. Search strategies were adapted for each cancer type and included studies published in the last 10 years with patients aged≥65 years. Eligible studies assessed frailty using any defined method and reported outcomes, such as treatment tolerance, survival, functional decline, or complications. A total of 48 studies were included (eight lung, 17 colorectal, seven prostate, and 16 hematological). The prevalence of frailty ranged widely from 4% to 81%, depending on the tools used. The most common instruments were the G8 (a screening tool), mFI, Fried phenotype, and Clinical Frailty Scale (CFS). Several studies misclassified screening instruments or prognostic scores as frailty measures. Frailty was consistently associated with poorer survival, increased postoperative complications, greater toxicity, and higher healthcare utilization across tumor types. However, the variability in frailty definitions and assessment tools limits direct comparisons and clinical implementation. Harmonization of definitions and routine integration of standardized geriatric tools are needed to strengthen the role of frailty in oncological decision-making.