Expression of SIALYL-Le(x) antigen defined by MAb AM-3 is an independent prognostic marker in colorectal carcinoma patients.

Expression of mucin-bound sialyl-Le(x) antigen during the progression of colorectal carcinoma and its potential prognostic value were analysed in sections of tumours from 182 patients with a documented follow-up by immunohistochemistry using the monoclonal antibody (MAb) AM-3. Two groups of colonic carcinomas with weak (n = 79) and strong (n = 103) sialyl-Le(x) expression were discerned. The percentage of strongly expressing tumours increased with the progression of the disease (UICC stage I = 10%, stage II = 46%, stage III = 63%, stage IV = 68%, p < 0.0001). Seventy-four percent of patients with carcinomas exhibiting a strong sialyl-Le(x) expression but only 34% of patients with weak sialyl-Le(x) expression died of the disease (p = 0.0026). In multivariate analysis, strong sialyl-Le(x) expression increased the relative risk of cancer-related death 3.8-fold (95% CI = 1.8-7.9, p = 0.00034). The separate analyses of patients in UICC stage II (n = 56), III (n =5 9) and IV (n = 57) revealed that strong sialyl-Le(x) expression was associated with a reduction of the 5-year overall survival rate in UICC stage II (84% vs. 54%, p = 0.0013) and in stage III patients (86% vs. 35%, p = 0.0008) after curative resection but was not relevant in patients with distant metastases. In conclusion, the strong expression of sialyl-Le(x) antigen defined by the MAb AM-3 in colorectal carcinomas is an independent unfavourable prognostic factor after curative resection in stage II and III patients. The predictive power of the sialyl-Le(x) expression may be helpful to define subgroups of patients at high risk for whom preventive adjuvant therapy can be selectively applied before the occurrence of detectable metastases. Copyright 2000 Wiley-Liss, Inc.