Selection of patients with monoclonal gammopathy of undetermined significance is mandatory for a reliable use of interleukin-6 and other nonspecific multiple myeloma serum markers

Systematic review of the association between circulating interleukin-6 (IL-6) and cancer

Our aim was to systematically review the epidemiologic evidence for an association of circulating interleukin-6 (IL-6), an inflammatory cytokine and cancer. We systematically searched electronic databases Embase, Medline and Web of Science for the studies of circulating IL-6 and any form of cancer. We identified and reviewed 189 discrete studies, consisting of 177 prevalent studies and three prospective studies. Cancer patients' IL-6 concentrations were higher than healthy controls' in most studies, but the results of investigations comparing IL-6 in cancer patients and individuals with benign diseases were less consistent. Due to the small number of prospective studies it is impossible to determine whether IL-6 is causally related to cancer. Large prospective studies of circulating IL-6 or studies using the functional variants of the IL-6 gene as instruments for circulating IL-6 concentrations would provide information on possible aetiological links between IL-6 and malignancy.

A systematic review of the association between circulating concentrations of C reactive protein and cancer

The objective of this study was to review and summarise the published evidence for an association between circulating concentrations of C reactive protein (CRP) and cancer through a systematic review. 90 discrete studies were identified. 81 (90%) were prevalent case-control or cross-sectional studies, and only 9 studies had a prospective design. In most prevalent studies, CRP concentrations were found to be higher in patients with cancer than in healthy controls or controls with benign conditions. Of the nine large prospective studies identified in this review, four reported no relationship between circulating CRP levels and breast, prostate or colorectal cancers, and five studies found that CRP was associated with colorectal or lung cancers. Most of the studies evaluating CRP as a diagnostic marker of cancer did not present relevant statistical analyses. Furthermore, any association reported in the prevalent studies might reflect reverse causation, survival bias or confounding. The prospective studies provided no strong evidence for a causal role of CRP in cancer. Instead of further prevalent studies, more large prospective studies and CRP gene-cancer association studies would be valuable in investigating the role of CRP in cancer.

Serum interleukin-6 has no discriminatory role in paraproteinaemia nor a prognostic role in multiple myeloma

We determined interleukin-6 (IL-6) levels in the serum of 212 well-defined patients with newly diagnosed paraproteinaemia and evaluated its discriminatory value and prognostic role in multiple myeloma (MM). Results were compared with serum neural cell adhesion molecule and beta-2-microglobulin, both established prognostic MM markers. Paraproteinaemia-related diagnoses were: MM (60), other haematological diseases (46), solid tumours (35), autoimmune diseases (17) and monoclonal gammopathy of unknown significance (MGUS) (54). The range of IL-6 levels in all diagnostic groups overlapped widely and did not serve as a discriminatory marker in newly diagnosed paraproteinaemia even when patients with infection or fever (42) were excluded. In MM high IL-6 levels (>/= 50 pg/ml) were not associated with a shorter survival (P = 0.24). We compared our results with 20 published studies on serum IL-6 in paraproteinaemia and/or MM. IL-6 data have to be related to the assay used (bio- or immunoassay) and to the status of MM (newly diagnosed, during therapy, progressive disease). We conclude that serum IL-6 is not specific for paraproteinaemia-related diseases and will not serve as a reliable discriminatory or prognostic marker in paraproteinaemia and MM.