Recent reflections on tumor markers

The necessity for monitoring serum levels of alphafetoprotein (AFP) and human chorionic gonadotropin (hCG) in patients with testicular cancer is widely known, but a few questions remain unanswered. Cross-reactivity of commercial hCG assays with luteinizing hormone remains a problem; and as patients apparently cured of testicular cancer age, they become subject to other diseases that can elevated AFP or hCG levels, creating confusion. There still are no adequate studies of the role of markers in staging, a problem that has become acute with the introduction of expectant treatment for metastases in clinical stage A disease. Calculation of the metabolic half-life of markers can be helpful in staging postoperatively, but calculations of the actual half-life of markers during induction chemotherapy is less useful than had once been hoped. Attempts to capitalize on the molecular heterogeneity of AFP have had little success, although newer analytic methods may change this; but ultrasensitive assays for urinary hCG are beginning to show promise. Studies of radioimmunodetection with anti-marker antibodies have been both encouraging and frustrating; the newly available monoclonal anti-marker antibodies may improve the results and also offer a possible means of improving chemotherapy. Placental alkaline phosphatase continues to look like a useful marker for seminoma, and lactic dehydrogenase is often helpful in all types of testicular cancer, especially in high-stage disease.