Cancer‐related fatigue: Towards a more targeted approach based on classification by biomarkers and psychological factors

Abstract Cancer‐related fatigue is a frequent, burdensome and often insufficiently treated symptom. A more targeted treatment of fatigue is urgently needed. Therefore, we examined biomarkers and clinical factors to identify fatigue subtypes with potentially different pathophysiologies. The study population comprised disease‐free breast cancer survivors of a German population‐based case‐control study who were re‐assessed on average 6 (FU1, n = 1871) and 11 years (FU2, n = 1295) after diagnosis. At FU1 and FU2, we assessed fatigue with the 20‐item multidimensional Fatigue Assessment Questionnaire and further factors by structured telephone‐interviews. Serum samples collected at FU1 were analyzed for IL‐1ß, IL‐2, IL‐4, IL‐6, IL‐10, TNF‐a, GM‐CSF, IL‐5, VEGF‐A, SAA, CRP, VCAM‐1, ICAM‐1, leptin, adiponectin and resistin. Exploratory cluster analyses among survivors with fatigue at FU1 and no history of depression yielded three clusters (CL1, CL2 and CL3). CL1 (n = 195) on average had high levels of TNF‐α, IL1‐β, IL‐6, resistin, VEGF‐A and GM‐CSF, and showed high BMI and pain levels. Fatigue in CL1 manifested rather in physical dimensions. Contrarily, CL2 (n = 78) was characterized by high leptin level and had highest cognitive fatigue. CL3 (n = 318) did not show any prominent characteristics. Fatigued survivors with a history of depression (n = 214) had significantly higher physical, emotional and cognitive fatigue and showed significantly less amelioration of fatigue from FU1 to FU2 than survivors without depression. In conclusion, from the broad phenotype “cancer‐related fatigue” we were able to delineate subgroups characterized by biomarkers or history of depression. Future investigations may take these subtypes into account, ultimately enabling a better targeted therapy of fatigue.