A novel sialyl Le(X) expression score as a potential prognostic tool in colorectal cancer

BACKGROUND: Treatment decisions in colorectal cancer subsequent to surgery are based mainly on the TNM system. There is a need to establish novel prognostic markers based on the molecular characterization of tumor cells. Evidence exists that sialyl Le(X) expression is correlated with an unfavorable outcome in colorectal cancer. The aim of this study was to establish a simple sialyl Le(X) staining score and to determine a potential correlation with the prognosis in a series of advanced colorectal carcinoma patients. METHODS: In order to implement routine use of sialyl Le(X) immunohistology, we established a new, easily reproducible score and defined a cutoff which discriminated groups with better or worse outcome, respectively. We then correlated sialyl Le(X) expression of 215 UICC stage III and IV patients with disease-free and cancer-related survival. RESULTS: A five-stage score could be established based on automated immunohistochemical stainings. Using a statistical model, we calculated a cutoff to discriminate between weak and strong staining positivity of sialyl Le(X). Patients with strong positive specimens had a worse cancer-related survival (P = 0.004) but no difference was observed for disease-free survival (P = 0.352). CONCLUSIONS: These results demonstrate a strong correlation between high sialyl Le(X)-expression in colorectal carcinomas and cancer-related survival. Our highly standardized and easy-to-use staining score is suitable for routine use and hence it could be recommended to evaluate sialyl Le(X)-expression as part of the standard histopathological analysis of colorectal carcinomas and to validate the score prospectively based on a larger population.