Inflammatory biomarkers for persistent fatigue in breast cancer survivors.
OBJECTIVE
This study seeks to define immunologic and inflammatory variables associated with persistent post-treatment fatigue in breast cancer survivors.


METHODS
Leukocyte subsets, plasma inflammatory markers, and ex vivo proinflammatory cytokine production were assessed in 50 fatigued and nonfatigued breast cancer survivors recruited > or = 2 years after successful primary therapy. Multivariate statistical analyses were used to define a composite immunologic biomarker of fatigue risk.


RESULTS
Fatigued breast cancer survivors were distinguished from nonfatigued survivors by increased ex vivo monocyte production of interleukin (IL)-6 and tumor necrosis factor-alpha following lipopolysaccharide stimulation, elevated plasma IL-1ra and soluble IL-6 receptor (sIL-6R/CD126), decreased monocyte cell-surface IL-6R, and decreased frequencies of activated T lymphocytes and myeloid dendritic cells in peripheral blood (all P < 0.05). An inverse correlation between sIL-6R and cell-surface IL-6R was consistent with inflammation-mediated shedding of IL-6R, and in vitro studies confirmed that proinflammatory cytokines induced such shedding. Multivariate linear discriminant function analysis identified two immunologic markers, the ratio of sIL-6R to monocyte-associated IL-6R and decreased circulating CD69+ T lymphocytes, as highly diagnostic of fatigue (P = 0.0005), with cross-validation estimates indicating 87% classification accuracy (sensitivity = 0.83; specificity = 0.83).


CONCLUSIONS
These results extend links between fatigue and inflammatory markers to show a functional alteration in proinflammatory cytokine response to lipopolysaccharide and define a prognostic biomarker of behavioral fatigue.
Collado-Hidalgo
Alicia
A
Cousins Center for Psychoneuroimmunology, University of California at Los Angeles Semel Institute for Neuroscience and Human Behavior, Los Angeles, California 90095-7076, USA.
Bower
Julienne E
JE
Ganz
Patricia A
PA
Cole
Steve W
SW
Irwin
Michael R
MR