DYNAMIC USE OF TUMOR-MARKERS, RATIONALE CLINICAL-APPLICATIONS AND PITFALLS

The dynamic evaluation of tumor markers is a promising area of investi gation which is expected to provide clinical information when serial s amples are available from the same patient. This is feasible in the po st-operatory evaluation, during the follow-up after the treatment for to the primary tumor and in the monitoring of the treatment for metast atic disease. Variations among serial samples may be assessed using bo th empirical and mathematical approaches. Empirical approaches rely on overcoming a given percentage usually chosen on the base of arbitrary decisions. Mathematical approaches include the actual half-life, the doubling time, a dose/time regression analysis and the calculation of the critical difference. The two former are currently used in clinical practice whereas the tow latter are still matter of investigation. As concerns the assessment of the radicality of the surgery for the prim ary tumor, the serum markers are used in germ cell tumors and in prost ate cancer. The half-life of the markers is the decision criteria used in germ cell cancers, while in prostate cancers PSA is expected to be undetectable more than 30 days after the radical prostatectomy. Tumor markers are currently used during the follow-up of several malignanci es after the treatment for primary tumor. Although several samples are available, decision criteria are still based on positive/negative cut -off values in severals instances. Promising dynamic approaches are un der investigation and are expected to lead to earlier and probably mor e accurate information concerning the disease progression. A critical point still under debate is the actual impact of tumor markers on pati ents' survival in malignancies incurable when metastatic, such as colo rectal cancer and breast cancer. This matter urgently demands perspect ive clinical studies. Finally, the dynamic use of tumor markers is nw commonly applied in the monitoring of the therapy for metastatic malig nancies. In this clinical setting mathematical criteria are used for o varian and germ cell tumors with promising results. Nevertheless, he u se of empirical criteria, namely the percentage of variation between t wo consecutive samples, is successfully used for the monitoring of the therapy of metastatic breast cancer. In conclusion, when several samp les are available from an individual patient they may be evaluated acc ording to dynamic criteria instead of referring to a conventional post ive/negative cut-off point. Although mathematical decision criteria ar e expected to provide more reliable data, empirical approaches are use d as well and provide useful information in decision making.