Physical Functioning in Older Breast Cancer Survivors

Abstract

The largest age group of breast cancer survivors (BCS) in the U.S. is comprised of women ages 65+, who are susceptible to age-related decrements in physical function accelerated by cancer treatment toxicities. Though exercise is known to reverse age-related functional limitations, older BCS may be heterogeneous in baseline functioning which may affect the efficacy of exercise to reverse functional declines. PURPOSE: Determine the efficacy of each aerobic and resistance training to improve physical function in older BCS, considering baseline physical functioning. METHODS: Older, early-stage, BCS (mean age=72), who underwent chemo- or radio-therapy in the previous 2 years were randomized to 12 months of supervised, group aerobic (AER) or resistance (RES) training or control (CON) flexibility exercise, followed by 6 months of home-based training. Physical function was assessed by the Physical Performance Battery (PPB), 5x chair stand time (sec), maximum bench and leg press (kg), and 4-meter usual walk speed (m/sec) tests and self-reported lower-body function with the Late-Life Function and Disability Instrument (LLFDI). A linear mixed effects model was used to assess function after 12 and 18 months on the full sample and only in BCS with PPB scores ≥9. RESULTS: 114 BCS were enrolled and randomized to AER (n=37), RES (n=39), or CON (n=38). Within the full sample there was a significant improvement in bench press strength at 12 months (p=0.03) and PPB at 18 months in RES vs CON. After removing participants with low baseline physical functioning (n=79), the following additional significant differences were found between: 1) RES (αmean=2.72±1.7) and CON (αmean=-3.06±2.0) for self-report physical function at both 12 (p=0.04) and 18 months (p=0.005), 2) AER (αmean=0.4±0.0) and CON (αmean=-0.03±0.0) at 12-months for average walk speed and, 3) AER (αmean=0.32±0.3) and RES (αmean=0.50±0.2) at 18 months, for chair time (p=0.05). CONCLUSIONS: Although AE and RT are efficacious in improving physical function in older BCS across a range of baseline physical functioning, broader improvements may only be possible among women with better functioning and thus capable of achieving a greater dose of exercise. Older BCS may need to be stratified into groups based on their initial functioning, then matched to appropriate training.