Understanding the Effects of Cancer‐Related Factors on the Association Between Physical Activity, Self‐Efficacy and Exercise Barriers Among Breast Cancer Survivors

BACKGROUND: Breast cancer can negatively impact survivors' physical activity (PA). Social cognitive theory (SCT) constructs may be correlated with PA, but it is unclear if cancer-related factors affect these relationships. AIMS: To examine associations between PA, self-efficacy, social support, and exercise barriers interference in breast cancer survivors and whether cancer-related factors moderate these relationships. METHODS: Baseline data from 341 post-primary treatment breast cancer survivors in a web-based diet/exercise intervention trial were analyzed. SCT constructs, accelerometry-measured and self-reported moderate-to-vigorous physical activity (MVPA), and cancer-related factors (stage, time since diagnosis, history of chemotherapy, history of radiation, and hormone therapy status) were examined using Pearson correlation analysis and multivariable linear regression analyses. RESULTS: Exercise barriers interference was inversely associated with self-reported (r = -0.272, p < 0.001); and accelerometry-measured MVPA (r = -0.128, p = 0.020). No other statistically significant associations were found. Stage and history of chemotherapy moderated the association between social support and self-reported MVPA. The association was stronger among survivors diagnosed with DCIS/stage I versus stage II/III (β = 4.14, p = 0.043, CI = -2.20-10.49) and weaker among individuals who previously received chemotherapy versus no chemotherapy history (β = -5.02, p = 0.026, CI = -11.51-1.47); effects were independent of one another. CONCLUSIONS: Cancer stage and previous chemotherapy moderate the association between social support and MVPA. Targeting social support in early-stage breast cancer survivors or survivors that did not receive chemotherapy may improve intervention effectiveness.