Social Support and Chemotherapy-Induced Peripheral Neuropathy in Breast Cancer: A Full Mediation Dual-Pathway Model Through Physical Activity and Psychological Distress.

[BACKGROUND] Chemotherapy-induced peripheral neuropathy (CIPN) is a debilitating toxicity. While social support is protective, its precise mechanisms remain unclear.

[AIMS] To test whether social support influences CIPN symptoms through physical activity and psychological distress, and if mediation is full or partial.

[METHODS] A prospective cohort of 240 breast cancer patients was enrolled and assessed longitudinally at three time points: baseline, 6 weeks, and 12 weeks. Using structural equation modeling, a partial mediation model (with a direct social support-CIPN path) was compared to a full mediation model (path constrained) via a likelihood ratio test. Indirect effects were tested with bootstrapping.

[RESULTS] Model comparison supported the full mediation (Δχ(1) = 0.22, p = 0.639). Higher baseline social support was associated with greater week-6 physical activity (β = 0.668) and lower week-6 psychological distress (β = -0.602). These mediators subsequently predicted week-12 CIPN symptoms (physical activity: β = -0.403; psychological distress: β = 0.361). Significant indirect effects were found for both the physical activity pathway (β = -0.271) and the psychological distress pathway (β = -0.219). The model explained 47.6% of the variance in CIPN symptoms.

[CONCLUSIONS] The protective effect of social support on CIPN symptoms operates predominantly by promoting physical activity and buffering psychological distress. These findings support integrated, mechanism-informed interventions leveraging social resources to mitigate a debilitating burden of treatment-related symptoms.