title: Prognostic significance of early serum tumor marker half-life in metastatic testicular teratoma.
abstract: OBJECTIVE
  To determine whether the initial regression rates of serum tumor marker concentration (alpha-fetoprotein [AFP] and beta-human chorionic gonadotrophin [HCG]) were important prognostic factors after chemotherapy for germ cell tumors.
  
  
  METHODS
  The analysis was confined to patients with at least two precise marker assay results between days 7 and 22 from start of platinum-based combination chemotherapy, with at least 7 days between markers. One hundred eighty-three patients 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 = Ln1/2/G, where G was the gradient of the marker slope on a plot of Ln marker concentration versus time. MHL was regarded as prolonged if more than 3 days for HCG or more than 7 days for AFP.
  
  
  RESULTS
  The median AFP MHL was 6 days (range, 2.7 to 237) and the median HCG MHL was 2.6 days (range, 1.7 to 37.5). Forty-nine of 142 patients (35%) had a prolonged AFP MHL; 39 of 111 patients (35%) had a prolonged HCG-MHL. A prolonged MHL did not identify relapse after front-line chemotherapy. The positive predictive value of MHL tests in identifying 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 again the positive predictive value of this test was only 23%.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Academic Unit of Radiotherapy and Oncology, Royal Marsden Hospital, Surrey, United Kingdom.
authors.forename: M J
authors.initials: MJ
authors.lastname: Stevens
authors.forename: A R
authors.initials: AR
authors.lastname: Norman
authors.forename: D P
authors.initials: DP
authors.lastname: Dearnaley
authors.forename: A
authors.initials: A
authors.lastname: Horwich
mesh_terms: D000293:Adolescent; D000328:Adult; D014408:Biomarkers, Tumor / Q000097:blood*; D006063:Chorionic Gonadotropin / Q000097:blood*; D018997:Chorionic Gonadotropin, beta Subunit, Human; D018572:Disease-Free Survival; D006207:Half-Life; D006801:Humans; D008297:Male; D008875:Middle Aged; D010446:Peptide Fragments / Q000097:blood*; D011379:Prognosis; D013724:Teratoma / Q000097:blood* / Q000188:drug therapy / Q000401:mortality / Q000473:pathology / Q000556:secondary; D013736:Testicular Neoplasms / Q000097:blood* / Q000188:drug therapy / Q000401:mortality / Q000473:pathology; D000509:alpha-Fetoproteins / Q000032:analysis*
chemical_list: D014408:Biomarkers, Tumor; D006063:Chorionic Gonadotropin; D018997:Chorionic Gonadotropin, beta Subunit, Human; D010446:Peptide Fragments; D000509:alpha-Fetoproteins