The use of tumour markers in clinical practice

Abstract

The value of any circulating tumour marker depends on its relative merits in screening for asymptomatic disease, use in diagnosis of a particular cancer, being able to predict extent of disease and hence prognosis, and in monitoring disease response to treatment. In this respect human chorionic gonadotrophin has all the attributes of the ideal tumour marker for the gestational trophoblastic tumours. It seems unlikely that a specific tumour marker will be found for colorectal cancer. Of the available colorectal tumour markers, CEA meets the requirements most closely when employed as a single agent, and as it has been around for 25 years all newer tumour markers are naturally compared to this standard. Monoclonal antibodies have proved to be disappointing as a screening agent, although they are associated with fewer false positive results. In view of the well known heterogeneity of antigen expression within a single tumour, panels of monoclonal antibodies (i.e. pre-defined antisera) may be more useful than a single antibody. Proteins, enzymes and other antigens are generally too non-specific to be of any clinical use in colorectal cancer.