High serum concentrations of sialyl Lewisx predict multilevel N2 disease in non-small-cell lung cancer

Background: The purpose of this study was to analyze the clinical significance of serum Sialyl Lewis(x) (SLX) concentrations as a predictor of N2 disease in patients with non-small-cell lung cancer. Methods: The study included 272 patients with non-small-cell lung cancer who underwent pulmonary resection in our institution between January 1998 and December 2003. Of 272 patients, the serum concentrations of SLX were measured by using a commercially available radioimmunoassay kit. Results: The 5-year survival rates of patients with concentrations of SLX > 38 U/mL and those with lower concentrations were 32% and 69%, respectively (P < .0001). The median serum concentration of SLX in patients with multilevel N2 or N3, single-level N2, and N0/1 disease were 44, 30, and 27 U/mL, respectively. The concentrations of serum SLX in patients with multilevel N2 disease were significantly higher than those in patients with single-level N2 or those with N0/1 disease (Mann-Whitney U-test; P < .0001). Although the sensitivity of SLX for identifying patients with non-small-cell lung cancer was only 24% in all patients, the sensitivity of SLX increased as the N-factor increased; the sensitivity of N0/1 disease was 15%, that of single-level N2 disease was 22%, and that of multilevel N2 or N3 disease was 71%. Conclusions: High serum concentrations of SLX predicted multilevel N2 disease and the associated poor outcome. Although the sensitivity of serum SLX is not acceptable for use as a screening tumor marker, we suggest that the serum concentration of SLX is useful as a staging marker to determine the strategy of treatment.