Objective: Fatigue is currently recognized as an undertreated symptom in cancer. To date the association between fatigue and inflammatory activation has not been examined in patients with advanced cancer. Our exploratory investigation considered whether variations in routinely available hematological parameters relate to the severity of fatigue reports.
Methods: Fatigue, white blood cell differential, and hemoglobin concentration were assessed in 44 Stage IIIb and IV non-small-cell lung cancer (NSCLC) patients. Days of survival and the relative timing of treatment discontinuation were also recorded. Relationships between fatigue intensity and length of survival and between fatigue and hematological variables were examined using binomial and linear regressions respectively.
Results: When we controlled for effects related to age, gender, and time until treatment termination, more intense fatigue was associated with shorter survival (beta = -.34, p = .03). Lower hemoglobin concentrations were associated with more intense fatigue (beta = -.36, p = .04). When we controlled for the effect attributable to hemoglobin, higher neutrophil (beta = .43, p = .01) and monocyte (beta = .31, p = .05) concentrations were associated with reports of more severe fatigue.
Significance of results: This exploratory study provides empiric data showing that the severity of fatigue reported by advanced-stage NSCLC patients is significantly associated with length of survival. Consistent with existing data, linear regression identified a negative association between fatigue intensity and hemoglobin concentration. When we controlled for this effect, further linear regressions identified significant relationships between fatigue and blood concentrations of neutrophils and monocytes. Further, the magnitude of relationship between myeloid cell concentrations and fatigue was similar to the effect size identified for the relationship between hemoglobin and fatigue. Thus, the indirect measure of inflammatory state provided by routinely assessed myeloid cell counts appears to play as strong a role as the established variable, hemoglobin, in accounting for the fatigue reported by this sample of advanced-stage lung cancer patients.