Methodologic issues in the measurement of cytokines to elucidate the biological basis for cancer symptoms.

Multiple concurrent symptoms are highly prevalent in patients with cancer. However, little is known about the relationships among these symptoms and their underlying mechanisms. A number of cytokines that are involved in the development of sickness behavior are hypothesized to be a mechanism for symptom clusters. Measurement of these cytokines would provide valuable information that could be used to elucidate mechanisms underlying the development of symptom clusters and the identification of potential targets for intervention studies. In this article, the authors explore several issues that warrant careful consideration when designing a research study involving the use of a cytokine as a biomarker in symptom cluster research. These issues include which molecules to measure, which specimens to collect, the timing of specimen collection and processing, and which technologies to use to measure the biomarker and the sensitivity and specificity of the assay system. The article begins with a brief discussion of cytokines and sickness behavior and the role of the cytokines in cancer-related symptoms.