[Future prospects for the use of tumor markers]

The prospects for the implementation of tumour markers in the immediate future depend amongst other factors on the provision of adequate clarification of the situation for clinicians. Both uncritical overestimation, as well as ignorance-based rejection block the employment of these methods at the expense of the availability of up-to-date treatment for cancer patients. Furthermore, an optimization of the use of the currently-available tumour marker assays has to be postulated. A prerequisite for such an optimization programme is further knowledge of the stability of the expression pattern of tumour-associated markers in a particular tumour. First, evidence for a shift in marker expression pattern in lung cancer patients is represented and possible consequences for post-therapeutic monitoring are discussed. Evaluation of marker determinations is difficult for many markers due to our ignorance of the biological function of the corresponding compounds. It is postulated, therefore, that further developments should focus on compounds with better-understood biological functions. Recent work on cGMP, transforming growth factor alpha (TGF alpha) and oncogene products are discussed in this light. Determination of the products of transforming oncogenes with the aid of monoclonal antibodies may permit the development of tumour specific markers. In the case of human tumours, the ras-gene products seem to be promising candidates. The product of the erbB-2 seems to be another interesting candidate, since this gene has been shown to be frequently overexpressed in the case of human malignancies. Finally, recent developments in the area of anti-oncogenes (tumour-suppressor genes) may open additional diagnostic avenues. Determination of anti-oncogene deletions may become an important new approach in tumour prevention.