Determinants of physical, affective, and cognitive fatigue during breast cancer therapy and 12 months follow-up.

Fatigue is common in cancer survivors but often insufficiently treated. Due to its complexity a one-size-fits-all treatment seems not appropriate. To gain more information on influencing factors and sub-dimensions of fatigue we investigated potential determinants and correlates of physical, affective, and cognitive fatigue in breast cancer survivors during and after adjuvant therapy. Within the follow-up of two randomized controlled trials physical, affective, and cognitive fatigue were repeatedly assessed during and up to 12 months after cancer therapy with the 20-item Fatigue Assessment Questionnaire in 255 breast cancer survivors. Determinants of the different fatigue dimensions over time were explored with linear mixed models. Chemotherapy appeared as significant precipitating factor for physical fatigue. However, type of cancer therapy had no impact on fatigue one year post-treatment. Obesity was significantly associated with increased physical fatigue throughout all time points (Δ=15.5 at 12 months) whereas exercise appeared to be beneficial (Δ = -6.3). In contrast, affective fatigue was significantly associated with poor social support and worries about the future. In addition, poor sleep quality and previous use of psychopharmaceuticals were significantly associated with physical, affective, as well as cognitive fatigue. Further, hot flashes were associated with increased physical and cognitive fatigue. In conclusion, the broad diagnosis 'fatigue' in cancer survivors needs to be recognized as a diversity of symptoms determined by specific characteristics and likely different etiologies. Taking potential influencing factors such as obesity, physical inactivity, sleep problems, hot flashes, lack of social support, or psychological disorders into consideration might enable a better, individually-tailored fatigue treatment.