Contemporary North-American population-based validation of the International Germ Cell Consensus Classification for metastatic germ cell tumors of the testis

Background The International Germ Cell Consensus Classification (IGCCC) is the recommended stratification scheme for newly diagnosed metastatic seminoma (mSGCT) and non-seminoma germ cell tumor (mNSGCT) patients. However, a contemporary North-American population-based validation has never been completed and represented our focus. Materials and methods We identified mSGCT and mNSGCT patients within the SEER database (2004-2015). The IGCCC criteria were used for stratification into prognostic groups. Kaplan-Meier (KM) derived actuarial 5-year overall survival (OS) rates were calculated. In addition, cumulative incidence plots tested cancer-specific (CSM) and other-cause mortality (OCM) rates. Results Of 321 mSGCT patients, 190 (59.2%) and 131 (40.8%), respectively, fulfilled good and intermediate prognosis criteria. Of 803 mNSGCT patients, 209 (26.1%), 100 (12.4%), and 494 (61.5%), respectively, fulfilled good, intermediate, and poor prognosis criteria. In mSGCT patients, actuarial KM derived 5-year OS was 87% and 78% for, respectively, good and intermediate prognosis groups (p = 0.02). In cumulative incidence analyses, statistically significant differences were recorded for CSM but not for OCM between good versus intermediate prognosis groups. In mNSGCT patients, actuarial KM derived 5-year OS was 89%, 75% and 60% for, respectively, good, intermediate, and poor prognosis groups (p < 0.001). In cumulative incidence analyses, statistically significant differences were recorded for both CSM and OCM between good, intermediate, and poor prognosis groups. Conclusions Our findings represent the first population-based validation of the IGCCC in contemporary North-American mSGCT and mNSGCT patients. The recorded OM rates closely replicate those of the original publication, except for better survival of poor prognosis mNSGCT patients.