Association of Interleukin-6 and Other Cytokines with Self-Reported Pain in Prostate Cancer Patients Receiving Chemotherapy

Background. Pain is a common and dose-limiting side effect of many potentially curative cancer chemotherapeutic agents. This chemotherapy-induced pain (CIP) affects the quality of life of cancer patients and survivors and hampers the optimal clinical management of chemotherapy in cancer patients. The underlying mechanisms remain largely unknown, but changes in levels of cytokines/chemokines may contribute to the pathophysiology of CIP. Objective. This retrospective study was aimed at examining whether plasma levels of various cytokines change in prostate cancer patients after chemotherapy treatment and whether such changes (if any) are associated with their pain intensity. Methods. Using a Luminex assay, plasma levels of 27 cytokines/chemokines were measured in 78 men: 30 patients with metastatic prostate cancer who received chemotherapy (Docetaxel, 75mg/m 2 intravenously), 29 untreated patients with nonmetastatic prostate cancer, and 19 healthy controls. Subjective pain was assessed in chemotherapytreated cancer patients using the 11-point numeric rating scale (NRS) pain scores. Results. Chemotherapy-treated patients with pain (NRS 3) exhibited significantly increased levels of the pro-inflammatory cytokines (IL-6, IL-8) and chemokines (Eotaxin, VEGF, and IP-10) compared with untreated cancer patients or with patients without pain (NRS50). Of the 27 cytokines examined, only IL-6 was positively correlated with pain intensity in the chemotherapy-treated patients with pain. Conclusions. These findings suggest that the cytokines, particularly IL-6, whose levels were elevated in the chemotherapy-treated patients may be involved in the pathophysiology of CIP, and that they might be potential new targets for pain control in cancer patients receiving chemotherapy.