Patient-reported and objectively measured physical function in older breast cancer survivors and cancer-free controls

Objectives: Older breast cancer survivors (BCS) consistently report more functional limitations than women without cancer, but whether or not these differences remain when using objective measures of physical functioning and the correlates of these measures is unknown. Methods: Cross-sectional study comparing older (≥60 years old) BCS (n = 84) to similarly aged women without cancer (n = 40). Patient-reported physical function was assessed by the SF-36 physical function (SF-36PF) subscale and the Late Life Function & Disability Instrument (LLFDI). Objective measures included the short Physical Performance Battery (sPPB), usual walk speed (m/s), chair stand time (sec) and, grip strength (kg). Potential predictors included age, comorbidities, symptom severity, fatigue and skeletal muscle index (SMI; kg/m ² ). Results: Patient-reported physical function was significantly lower in BCS than controls using SF-36PF (47.3 ± 0.1 vs. 52.9 ± 4.0, p < 0.001) and LLFDI (68.2 ± 10.5 vs. 75.0 ± 8.9, p = 0.001). BCS had significantly lower sPPB scores (10.7 ± 0.1 vs. 11.7 ± 0.5, p < 0.001), longer chair stand times (12.6 ± 3.7 vs. 10.1 ± 1.4 s, p < 0.001), and lower handgrip strength (22.3 ± 5.0 vs. 24.3 ± 4.4 kg, p = 0.03) than controls, but similar walk speed (1.1+0.2 vs. 1.1+0.1 m/s, p = 0.75). Within BCS, age, comorbidities, SMI, symptom severity and fatigue explained 17.3%–33.1% of the variance across physical function measures. Fatigue was the variable most consistently associated with patient-reported physical functioning and age and comorbidities were the variables most consistently associated with objectively measured physical functioning. Conclusion: Older BCS should be screened for functional limitations using simple standardized objective tests and interventions that focus on improving strength and reducing fatigue should be tested.