Objective The Cancer and Aging Research Group (CARG) score was developed to predict severe chemotherapy-induced toxicity risk in older adults; validation study results have varied. The Tolerance of Anti-cancer Systemic Therapy in the Elderly study sought to evaluate the CARG score prospectively in a chemotherapy-naïve UK population.Methods and analysis This multicentre, prospective, observational study recruited patients aged ≥65 years commencing first-line chemotherapy for any solid organ malignancy or setting. Baseline demographics and established frailty measures were recorded. Follow-up data including toxicity and hospital admissions were collected retrospectively. Baseline CARG score predictive ability was assessed.Results 339 patients were recruited from 19 centres; median age 73 years (range 65–92), 51.9% male and 54.9% gastrointestinal primary. At baseline, 85% of patients were of Eastern Cooperative Oncology Group Performance Status (ECOG PS) 0–1, with median Rockwood Clinical Frailty Scale (CFS) 3 (range 0–8).314 (92.6%) patients had follow-up data; 69 (22.3%) patients experienced Common Terminology for Cancer Adverse Events grade ≥3 toxicity and 84 (27%) required hospital admission during treatment.Increasing CARG risk groups had increased grade ≥3 toxicity (low 19.6%, medium 22.2%, high 28.2%); however, this was non-significant with no evidence of robust predictive performance. Predictive performance of CFS and ECOG PS was superior to CARG. Importantly, patient and clinician perceptions of toxicity risk differed significantly.Conclusions In older UK patients with cancer commencing chemotherapy, baseline frailty was prevalent. CARG score did not robustly discriminate or predict high-grade toxicity risk. ECOG and CFS showed superior, although limited, ability to predict and discriminate. This study highlights the need for the development of tools that better predict toxicity in this population.
