Table 1.

Derivable frailty measures selected for evaluation: rationale, source and categorisation.

Frailty measure	Rationale for selection	Source of data	Type of data and categorisation
ECOG Performance Status	Used routinely in the assessment of fitness for SACT	Clinician-assessed prospectively	Categorical: scores 0, 1, 2 or > 2 – as collected in GO2 study [13]
GO2 Frailty Score [13]	Pre-determined geriatric assessment-based frailty measure for the GO2 study based on published literature [1]	Measured prospectively by assessing impairment (yes/no) in 9 frailty domains: weight loss, mobility, falls, neuropsychiatric, physical functioning, social functioning, mood, fatigue, and polypharmacy	Numeric: Number of domains with impairments, out of 9 Categorical: Not frail (0–1/9 domain impaired), Mildly frail (2/9 domains impaired), Severely frail (≥3/9 domains impaired) - as categorised in original publication [13]
‘Modified’ Clinical Frailty Scale	Global assessment of frailty, potentially easy to undertake but not yet tested in this setting	7-point scale based on the Rockwood Clinical Frailty Scale [4]. Derived retrospectively via an algorithm from questionnaire data regarding patients' function, fatigue and impact of symptoms/disease (supplement 1).	Numeric: Score 1–7 Categorical: Fit (1–2), Pre-frail (3–4), Frail (5+) – guided by feedback expert review and findings of statistical analysis
Geriatric-8[9]	Frailty screening tool recommended by ASCO consensus guidelines [8]	8-item questionnaire collected prospectively encompassing food intake, weight loss, mobility, neuropsychological problems, BMI, polypharmacy, self-rated health and age.	Numeric: Total score of 0–17 (lower scores align with adverse features) Categorical: >14 (‘normal’), ≤14 (‘abnormal’) – based on threshold to refer for GCA [9]
Cancer and Aging Research Group toxicity score [11]	Toxicity prediction tool recommended by ASCO consensus guidelines [8]	11 items encompassing age, cancer type, chemotherapy schedule, functioning, anaemia and kidney function. Derived retrospectively.	Numeric: Total score of 0–19 (higher scores reflecting adverse features). Categorical: Low risk (0–5), Medium risk (6–9), High risk (10–19) - based on published literaure [11]