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.