Immunoreactive interleukin-6 and acute phase proteins as prognostic factors in multiple myeloma

Abstract

High serum level of bioactive interleukin-6 (IL-6) is regarded as a predictor of poor prognosis in multiple myeloma (MM), On the other hand, the reported levels of immunoreactive IL-6 have been highly variable, and the prognostic value of immunoreactive IL-6 in MM is not clear. We have analyzed the prognostic significance Of serum immunoreactive IL-6, as measured by a sensitive immunosorbent assay, in 210 patients with newly diagnosed MM subsequently treated with intermittent melphalan and prednisone. The serum levels of acute phase proteins C-reactive protein (CRP), α1-antitrypsin (α1AT), and acid α1-glycoprotein (orosomucoid; OM) were evaluated as surrogates for IL-6. Serum IL-6, CRP, α1AT, and OM levels were raised in 42%, 40%, 41%, and 24% of the patients, respectively. There was a significant correlation between the clinical stage of the patients and serum IL-6 (P = .006), α1AT (P = .001), and OM (P = .004) levels at diagnosis. At 3 years, 52% of the patients were alive. Univariate logistic regression analysis showed that high levels of IL-6 (P = .002), CRP (P = .02), α1AT (P < .001), OM (P = .007), β2-microglobulin (β2M; P < .001), and thymidine kinase (P < .05) were all associated with 3-year mortality. In multivariate regression analysis, β2M (P < .0001) and α1AT (P = .01) had independent prognostic significance. The patients with high levels of both β2M and α1AT or IL-6 were at very high risk of dying within 3 years from diagnosis (16% and 21% of the patients in these groups were alive, respectively). When the patients were stratified according to the clinical stage, the prognostic significance of serum IL-6 and α1AT was especially evident in stage II patients. When the patients were divided into two groups according to normal or raised serum IL- 6 levels, the patients with high IL-6 levels had more frequent osteolytic bone lesions (P = .03) and a more aggressive disease. We conclude that serum immunoreactive IL-6 is a significant prognostic marker in MM.