Plasma interleukin-6 and fatigue in terminally ill cancer patients

Fatigue is one of the most distressing symptoms among terminally ill cancer patients. However, no effective intervention has been established. Several studies have suggested the role of cytokines in fatigue in cancer patients receiving anti-cancer treatment, patients with metastatic cancer, and cancer survivors, but not in terminally ill cancer patients. In the present study, the potential association between fatigue and plasma interleukin-6 (IL-6) was examined in 46 terminally ill cancer patients (median survival: 64.5 days) who received neither steroids nor nonsteroidal anti-inflammatory drugs. Fatigue was evaluated by the Cancer Fatigue Scale (CFS), which consists of multiple dimensions of fatigue, such as Physical, Affective, and Cognitive subscales. Plasma IL-6 levels were measured using an enzyme-linked immunosorbent assay and were compared between patients with and without "clinical fatigue" as defined by the total score of the CFS. Additionally, associations between each of the CFS scores and IL-6 levels were examined. As a result, the IL-6 level in patients with clinical fatigue (n = 27 [59%]; mean, SD, median, and range: 37.1, 46.4, 17.1, and 3.7-182.5 pg/ml, respectively) was significantly higher than those without clinical fatigue (n = 19 [41%]; mean, SD, median, range: 14.3, 12.2, 8.0, and 2.8-45.0 pg/ml, respectively) (P = 0.02). The IL-6 level significantly correlated with the Physical subscale score (r = 0.35, P = 0.02), but not with other subscale scores. In conclusion, IL-6 may play a role in fatigue, especially in the physical dimension, in terminally ill cancer patients. The results of the present study provide information to develop a new treatment strategy for cancer fatigue in terminally ill cancer patients.