Declines in Social Support During Breast Cancer Treatment and Their Association With Exercise Capacity Reductions in...

Breast cancer (BC) survival has improved but is often offset by adverse effects, including reduced exercise capacity. Research in the general population suggests that social support may mitigate exercise capacity declines. However, this relationship in BC survivors has not been examined. This analysis sought to examine relationships between social support overall (and within social support subscales) and exercise capacity declines at 3 months in BC survivors during treatment in relation to cancer-free controls. In 230 BC (stage I-III) survivors and 128 cancer-free controls within the UPBEAT Study (NCT02791581), submaximal exercise capacity and social support were obtained via 6-Minute Walk Distance (6MWD) and MOS Social Support survey, respectively, at baseline and 3 months. Linear regression examined associations between social support and 6MWD declines in BC survivors and controls at 3 months. Declines in 6MWD were associated with social support ( $\beta$ = 23.8; P = .03). Positive social interactions showed the greatest reduction during BC treatment (P = .02). Whereas no association was observed in controls, in BC survivors lower positive social interaction was associated with 6MWD declines ( $\beta$ = 23.8; P = .03; p _int = 0.02). The findings suggest the importance of social support, particularly positive social interactions, during BC treatment.