An international study evaluating the epidemiology of intracranial germ cell tumors in the native versus immigrant Japanese populations: the need for an international registry

Abstract

Background: Pediatric intra-cranial germ cell tumors (iGCTs) occur at an incidence of 0.6-1.2 cases/million/year in Western countries. The incidence is reported up to 5 times higher in Japan. It is unknown whether this increased incidence is due to genetic predisposition or environment.

Methods: The incidence of iGCTs in children ages 0-19 years was evaluated from December 1st, 1996-December 1st, 2016 in stable Japanese immigrant populations living abroad and compared to current native Japanese registry data. The incidence of medullobblastoma was used as a control to account for assumptions in the data. Sites were identified based on historical and population data of known large scale emigration from Japan during a period of industrialization from 1868-1912 which resulted in large, stable Japanese immigrant populations abroad. These three representative sites included Lima, Peru, San Paolo, Brazil, and Vancouver, Canada. Data was collected from registry and hospital-based resources within each region.

Results: A review of the Brain Tumor Registry of Japan from 1984-2004 revealed an incidence of 2.5 cases/million/year, lower than previously reported, and a lower incidence of medulloblastoma at 1.2 cases/million/year. Data from Vancouver, Canada, Lima, Peru, and San Paolo, Brazil included a total population of 731,174 Japanese persons. The ratio of all medulloblastoma to iGCT cases in Japan was identified as 1:2 while the ratio was 2:1, 6.5:1, and 5:1, respectively, in the other three locations. The data suggests increased incidence in native Japan may not translate to higher incidence in immigrant Japanese populations abroad and a clear genetic component was not found in our data set.

Conclusions: A more precise and comprehensive study is needed to determine the cause of this difference in incidence. This study also emphasizes the importance of national and state registries and is a call to collaborate on state and country level epidemiology studies.

Keywords: Epidemiology; Intracranial germ cell tumor; Japanese.