Cytokine levels during EBRT correlated with fatigue changes from baseline to one year post-EBRT. Among the 48 cytokines tested, concentrations of 9 cytokines (pg/ml) measured at midpoint of EBRT showed significant correlations with FACT-F score changes from T1 to T3: 1) proinflammatory cytokines IL3 (A; r = 0.44, p = .023), IL8 (B; r = 0.42, p = .028), IL16 (E; r = 0.49, p = .008), IFNα2 (G; r = 0.58, p = .002), IFNγ (H; r = 0.40, p = .033); 2) anti-inflammatory cytokine IL10 (D; r = 0.44, p = .021); 3) hematopoietic cytokines IL3 (A; r = 0.44, p = .023), IL9 (C; r = 0.44, p = .021); 4) IP10 (F; r = 0.43, p = .022), SDF1α (I; r = 0.49, p = .008).