PROGNOSTIC-SIGNIFICANCE OF EARLY SERUM TUMOR-MARKER HALF-LIFE IN METASTATIC TESTICULAR TERATOMA

Purpose: To determine whether the initial regression rates of serum tu mor marker concentration (alpha-fetoprotein [AFP] and beta-human chori onic gonadotrophin [HCG]) were important prognostic factors after chem otherapy for germ cell tumors. Patients and Methods: The analysis was confined to patients with at least two precise marker assay results be tween days 7 and 22 from start of platinum-based combination chemother apy, with at least 7 days between markers, One hundred eighty-three pa tients were eligible and marker half-life (MHL) was evaluated for AFP in 142 and for HCG in 111 cases, MHL was calculated from the following formula: MHL = Ln(1/2)/G, where G was the gradient of the marker slop e on a plot of Ln marker concentration versus time. MHL was regarded a s prolonged if more than 3 days for HCG or more than 7 days for AFP. R esults: The median AFP MHL was 6 days (range, 2.7 to 237) and the medi an HCG MHL was 2.6 days (range, 1.7 to 37.5). Forty-nine of 142 patien ts (35%) had a prolonged AFP MHL; 39 of 111 patients (35%) had a prolo nged HCG-MHL. A prolonged MHL, did not identify relapse after front-li ne chemotherapy. The positive predictive value of MHL tests in identif ying patients who progressed after front-line therapy was 18% for HCG, 20% for AFP, and 18% for either marker. A prolonged MHL did indicate a higher risk of mortality (hazards ratio [HR], 2.4; P = .016), but ag ain the positive predictive value of this test was only 23%. Conclusio n: Early evaluation of MHL by this method does not predict patients at higher risk of progression after front-line chemotherapy, and also is a poor guide to long-term prognosis.