Predictive value of interleukin-6 and neopterin in patients with multiple myeloma.

Concentrations of interleukin-6 and neopterin were measured in sera from 44 patients with multiple myeloma. To judge the relative prognostic value of these analyses, other clinical and laboratory variables were concomitantly determined. The patients were followed up to 9 years, and the abilities of all variables to predict outcome were assessed. Both neopterin (P = 0.0008) and interleukin-6 (P = 0.033) were significantly higher in patients with higher stages of the disease. The correlation between interleukin-6 and neopterin was weak but significant (Spearman's rank correlation coefficient, 0.38; P = 0.019). By univariate survival analysis using the product-limit approach, both neopterin (P = 0.0001) and interleukin-6 (P = 0.025) were identified as significant predictors of survival. Multivariate survival analyses by the proportional hazards technique demonstrated that either stage and neopterin or neopterin and interleukin-6 are useful combinations of predictor variables. Thus, interleukin-6, which is supposed to influence progression of multiple myeloma in an autocrine or paracrine manner, failed to contribute to prediction if stage was included in a model. In contrast, neopterin remained significant in all multivariate models.