Table 1.

Alternative measurement instruments of functional performance.

Assessment tool	Description	Nature of assessment	Feasibility	Limitations	Correlation with outcomes
KPS [3]	Linear scale from 0 (dead) to 100 (normally active, without evidence of disease) summarizing ability to perform daily activities, and level of assistance required	Subjective	Time to completion: minutes Easy to perform No equipment required	Poor reliability, variable levels of interobserver agreement Subjective, poor concordance between patient recorded and physician recorded KPS Poor predictor of prognosis when PS is good Poor sensitivity at the lower end of the scale Validated in a younger patient cohort and less applicable to an older heterogeneous patient group Unable to verify accuracy of assessment	Survival Prognosis Response to chemotherapy Chemotherapy toxicity Quality of life
ECOG PS [5]	6-point scale ranging from 0 (fully active) to 5 (dead), assessing level of function, ambulation, and capability of self-care	Subjective	Time to completion: minutes Easy to perform No equipment required	Poor reliability, variable levels of interobserver agreement Subjective, poor concordance between patient recorded and physician recorded KPS Poor sensitivity at the lower end of the scale Poor predictor of prognosis when PS is good Unable to verify accuracy of assessment	Survival Prognosis Response to chemotherapy Chemotherapy toxicity Quality of life
TUG [21]	Assessment of mobility and functional balance; functional mobility is quantified by the time it takes a patient to get up from a seated position, walk 3 meters, turn around, and return to a seated position	Objective	Time to completion: seconds Easy to perform Minimal equipment Required	Focused on one domain, mobility	Risk of falling Gait speed Residential status Ability to go outside alone safely Berg Balance Scale Barthel Index of Activity of Daily Living
Frailty Index (FI) [22]	FI is the ratio of the deficits present in a person to the total number of potential deficits evaluated	Subjective and objective components		Expensive	Mortality Predicts risk of adverse health outcomes
SPPB [23, 24]	SPPB measures physical and functional health and consists of three subtests: 4-meter walk, repeated chair stands, and standing balance	Objective	Time to completion: 5–10 minutes More complex assessment, 3 tests Minimal equipment required	Cost Inconvenient	Mortality (data available for older cancer patients and survivors)
EAM [25–27]	Wearable devices that objectively measure physical activity and can provide feedback	Objective	Time to completion: continuous assessment, duration dictated by patient Requires expensive equipment Feasibility and patient acceptability have been demonstrated	Cost Reduced accessibility Increased demand on healthcare computer information systems	Physical intervention, weight reduction Correlation with ECOG PS

KPS: Karnofsky Performance Status, ECOG PS: Eastern Cooperative Oncology Group, TUG: Timed Get Up and Go, SPPB: Short Physical Performance Battery, EAM: electronic activity monitoring, and PS: performance status.