Circulating cytokines as predictors of depression in patients with breast cancer

Depression is a common comorbid disorder associated with breast cancer, and it can have considerable physical and psychological impacts. Circulating cytokines have been proposed as a potential tool to predict depression in various diseases; however, limited studies have specifically examined it in breast cancer. In this study, we examined and compared the prediction ability of various circulating cytokines for depression in patients with breast cancer. Eighty-three patients with a new diagnosis of breast cancer not receiving chemotherapy were recruited; among them, 15 patients had depression and 68 did not have depression. Depression was evaluated using the Patient Health Questionnaire 9 (PHQ-9). Cytokine levels in the serum were measured using an immunology multiplex assay. Two types of cytokines were assayed: (1) proinflammatory cytokines (interleukin [IL]-1β, IL-2, IL-6, IL-12, IL-17A, interferon [IFN]γ, and tumor necrosis factor [TNF]α) and (2) anti-inflammatory cytokines (IL-4, IL-5, IL-10, and IL-13). Receiver operating characteristic (ROC) analysis was performed to calculate the area under the curves (AUCs), sensitivities, and specificities of circulating cytokines for predicting depression. As a result, IL-2 (AUC = 0.78) and IL-5 (AUC = 0.76) demonstrated good predictability for depression, even after controlling for the covariates (i.e. age, education, stage of cancer, surgery, radiation therapy, and hormone therapy). The optimal cut-off value of IL-2 for predicting depression was 1.06 pg/mL with a sensitivity of 86.7% and a specificity of 52.9%; this cytokine also had the best prediction ability in this study. Owing to the prediction ability and practical feasibility of circulating cytokines, they may be used as a valid laboratory diagnostic tool for depression in breast cancer.