Inflammation and dimensions of fatigue in women with early stage breast cancer: A longitudinal examination.

BACKGROUND: Fatigue is a common and long-lasting side effect of cancer. Although fatigue is a multidimensional symptom, biologic mechanisms of fatigue dimensions have not been identified. METHODS: Women recently diagnosed with early stage breast cancer (n = 192) completed assessments before and after adjuvant therapy and at 6-month, 12-month, and 18-month posttreatment follow-up visits. At each assessment, women completed the Multidimensional Fatigue Symptom Inventory and provided blood for protein markers of inflammation (tumor necrosis factor [TNF] alpha [TNF-α], soluble tumor necrosis factor receptor type II [sTNF-RII], interleukin 6 [IL-6], and C-reactive protein [CRP]). Mixed-effect linear models examined within-person and between-person associations between inflammatory markers and dimensions of fatigue. RESULTS: Analyses demonstrated a positive within-person association between general fatigue and TNF-α (b = 1.67; p = .037), sTNF-RII (b = 2.77; p = .002), and IL-6 (b = 0.86; p = .010) when controlling for age, race, education, body mass index, and cancer stage. Similarly, there was a positive within-person association between physical fatigue and TNF-α (b = 1.58; p = .007), sTNF-RII (b = 2.38; p < .001), and CRP (b = 0.43; p = .007). Conversely, there were negative within-person associations between emotional fatigue and TNF-α (b = -1.92; p = .004) and sTNF-RII (b = -2.10; p = .006). General and physical fatigue were positively associated with CRP at the between-person level (b = 0.82, p = .024 for general; b = 0.71; p = .012 for physical). No significant associations between mental fatigue and inflammatory makers were found. CONCLUSIONS: The current findings identified distinct dimensions of fatigue associated with inflammatory activity in women with breast cancer and highlighted individual variability in inflammatory markers as a key predictor of fatigue symptoms.