Fatigue in cancer patients compared with fatigue in the general United States population

BACKGROUND. Although fatigue is a common symptom among cancer patients, it is also a common experience in the general, healthy population. Its universality has made it difficult to appreciate whether the fatigue experienced by patients with cancer is distinguishable from the fatigue experienced by the general population. Because the etiology of fatigue is multifactorial, it also has been difficult to appreciate fully the relative contribution of anemia to cancer-related fatigue. METHODS. To address this issue, responses to a brief, standardized set of 13 questions from the Functional Assessment of Chronic Illness Therapy (FACIT) Measurement System were compared across three groups: anemic cancer patients (n = 2369 patients), nonanemic cancer patients (n = 113 patients), and the general United States population (n = 1010 persons). RESULTS. Fatigue scores of the anemic cancer patients (at both baseline and upon completion of anemia therapy) were significantly worse compared with the scores of nonanemic cancer patients that, in turn, were worse compared with the scores of the general United States population (P < 0.001). Score distributions were quite distinct for these three groups. Within the group of anemic cancer patients, the degree of anemia (mild, moderate, or severe) also was predictive of the degree of fatigue (P < 0.001), although the distributions were not dramatically distinct. CONCLUSIONS. Although anemia is clearly a factor that contributes to the severity of disease-related fatigue among cancer patients, hemoglobin levels explain only part of the difference compared with fatigue among the general United States population. The distinct distributions of fatigue scores of anemic cancer patients compared with the general United States population and the substantial sample sizes of these two groups enabled a discriminant analysis approach that allowed the differentiation of anemic cancer patients from the general population with high sensitivity (0.92) and reasonable specificity (0.69). Thus, although fatigue is a symptom most anyone can relate to, the fatigue of cancer patients, particularly those who are anemic, is decidedly worse. Interventions targeting this common and life-disrupting symptom likely would be of considerable value to patients with cancer.