α-Fetoprotein as a predictor of outcome for children with germ cell tumors: A report from the Malignant Germ Cell International Consortium

Background: There are several studies describing the correlation between unsatisfactory tumor marker decline and a poor prognosis for adult patients treated for germ cell tumors. In pediatric patients, the data are limited. Therefore, this study retrospectively analyzed data from Children's Oncology Group (COG) protocol AGCT0132 to determine whether a relationship exists between α-fetoprotein (AFP) decline and outcome. Methods: One hundred thirty-one patients with germ cell tumors who were enrolled in COG protocol AGCT0132 were eligible for this analysis of AFP decline. The serum AFP half-life was calculated from levels collected postoperatively as a baseline and after the start of chemotherapy. AFP decline was defined as automatically satisfactory (AFP normalized within the first 2 AFP measures after the start of chemotherapy), calculated satisfactory (AFP half-life ≤7 days after the start of chemotherapy), and unsatisfactory. Results: The 3-year cumulative incidence of relapse was 11% (95% confidence interval [CI], 6.0%-18%) for patients with a satisfactory decline and 38% (95% CI, 13%-64%) for patients with an unsatisfactory decline (P =.006). In stratified analyses, this effect was limited to patients who were 11 years of age or older and had standard risk 2 (SR2) disease (P =.004 and P =.007, respectively). Three-year overall survival (OS) for patients with a satisfactory decline versus an unsatisfactory decline was not statistically significant. Conclusions: This study is the first to show an association between AFP decline and the cumulative incidence of relapse in pediatric patients treated for germ cell tumors. Recognition of patients at high risk for relapse may allow for early intensification of therapy, which could affect future clinical trial design.