PROGNOSTIC-SIGNIFICANCE OF 5T4 ONCOFETAL ANTIGEN EXPRESSION IN COLORECTAL-CARCINOMA

The 5T4 oncofetal antigen is a 72 kDa glycoprotein defined by a monocl onal antibody raised against human placental trophoblast and is expres sed in many different carcinomas but detected only at low levels in so me normal epithelia. Immunohistochemical analysis of the patterns of e xpression in colorectal carcinomas has indicated a significant associa tion between the presence of the antigen in tumour cells and metastati c spread. The 5T4 antigen phenotype of 72 colorectal cancers has been compared with the clinical outcome of the patients in order to assess its relationship with prognosis. Forty per cent of tumours were 5T4 po sitive; the remainder were either unlabelled or exhibited stroma-assoc iated labelling only. There was a significant correlation between 5T4 expression in the malignant cells and unfavourable course of disease ( P<0.001). The 5 year survival with 5T4-positive tumours was 22% compar ed with 75% for patients with 5T4-negative tumours; median survival wa s 24 versus > 90 months respectively. Stratified analysis showed that 5T4 antigen tumour positivity was acting independently of each of stag e, site of tumour, age or sex. There were significant differences in s urvival for patients with Dukes' B and C stage carcinomas (P = 0.001 a nd P = 0.034). The results suggest that in colorectal cancer immunohis tochemical assessment of 5T4 expression may be useful in identifying p atients at high risk for tumour recurrence and for whom additional tre atment strategies might be most appropriate.