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. Int. J. Cancer 88:281–286, 2000. © 2000 Wiley-Liss, Inc.