In the immediate future it is necessary to solve three essential questions:
- The increase of specificity of tumor markers.
- The increase of sensitivity of tumor markers by the improvement of technical sensitivity and by the utilisation of product or quotient of two biomarkers. This improvement is, however, not sufficient neither for the screening of cancer, often nor for the early diagnosis of malignant tumors. It is caused mainly by the cell heterogeneity of primary tumor and its metastases, by the dependence of production of biomarkers on the phase of cell cycle, and by the different plasmatic halflife of tumor markers.
- The definition of several phases through which the work on tumor markers go (very similar to the examination and evaluation of new antineoplastic drugs). Initial examinations of its ability to discremnate between cancer and non-cancer, unfortunately, there are far fewer studies that go on to a second phase to determine more clearly the discriminatory value of a marker and to assess thoroughly the levels of markers in the whole spectrum of health and disease. For this, it is necessary to use age matched normal control patients with relevant benign diseases, other cancers, and various other appropriate controls. The next phase relates to the determination of the actual value of a marker for a particular clinical application. This is usually dependent on time consuming, expensive, and logistically difficult, well designed clinical trials and, therefore is approached only in a hadful of cases. Therefore, there is a great need for national and international cooperative studies.
The literature reflects feeling of pessimism or discouragement and of sustained optimism.
