Background: Interleukin-6 (IL-6) is a multifunctional cytokine that plays roles in the immune response, inflammation and hematopoiesis. Serum IL-6 levels have reported to reflect disease severity and high tumor burden in multiple myeloma (MM) patients and to correlate with several other laboratory parameters. Serum-soluble IL-6 receptor (sIL-6R) plays an agonist role in IL-6 signaling, enhancing its biological activity tenfold. PURPOSE-METHODS: We measured IL-6 and sIL-6R levels in 11 patients (7 male, 4 female, mean age 66.9 yr) with Waldenström's macrobulinemia (WM) using a commercially available enzyme-linked immunoassay in order to investigate their biological role and to find any possible relationship with disease severity, tumor burden or response to treatment.
Results: Serum IL-6 and sIL-6R concentrations at diagnosis were significantly higher than in healthy controls (Mann Whitney U-test, p < 0.001 and p < 0.01, respectively). Patients who were effectively treated had a significant reduction in IL-6 levels (p = 0.017). With regard to sIL-6R levels, no specific tendency was observed. In some of the responsive patients the levels increased whereas in others they decreased. No correlation was found between IL-6 and sIL-6R levels at diagnosis (p = 0.9, r = 0.036) or after treatment (p = 0.083, r = 0.3).
Conclusions: Our results suggest that IL-6 may be a marker reflecting tumor burden, disease severity and response to treatment in WM. With regard to sIL-6R, we believe that it does not seem to be of much value, and its role remains to be clarified. However, future studies are needed to confirm and further extend the present results.