Purpose: It has been suggested that interleukin-6 (IL-6) is a prognostic indicator for survival in patients with gastric carcinoma, but this has not been proved using survival analysis. In Asians, the -634G allele is associated with increased IL-6 production. The objective of this study was to evaluate the association between serum IL-6 levels, -634G/C polymorphism, and overall survival after resection for gastric carcinoma.
Experimental design: A total of 155 consecutive patients with gastric carcinoma were evaluated. Serum IL-6 levels were analyzed using an enzyme-linked immunoabsorbent assay. Genotype was determined by PCR and restriction fragment length polymorphism. Serum levels and survival were correlated with genotype and clinicopathologic factors.
Results: Age and stage, but not -634G/C genotype, were associated with serum IL-6 levels. The median survival for patients with stage II or stage III gastric carcinoma was 1,418 days in patients with low (< or =13 pg/mL) versus 618 days in patients with high (>13 pg/mL) serum IL-6 levels (P = 0.038). Results of a multivariate analysis showed that serum IL-6 level of >13 pg/mL was a significant predictor of poor survival (hazard ratio, 1.77; 95% confidence interval, 1.07-2.92; P = 0.026).
Conclusions: Serum IL-6 level of >13 pg/mL correlates with tumor progression and is an independent predictor of poor survival after resection. In patients with stage II and III gastric carcinoma, serum IL-6 level is more effective than stage as a prognostic indicator. By measuring IL-6, these patients can be divided into two groups with significant differences in survival. The -634G/C polymorphism is not associated with serum IL-6 level or survival.