Malignant extracranial germ cell tumors in the Netherlands between 1990 and 2018: Stable incidence and improved survival

Background: Population-based studies assessing long-term patterns of incidence and disease characteristics of germ cell tumors (GCTs) in children are scarce. We investigated incidence and survival trends of malignant extracranial GCTs in children using population-based nationwide data from the Netherlands. Methods: All malignant extracranial GCTs diagnosed in patients aged 0–18 years between 1990 and 2018 were selected from the Netherlands Cancer Registry. Incidence rates were calculated as the average annual number of cases per 1 million person-years. Five-year overall survival (OS) was calculated. Results: A total of 815 cases were identified. Gonadal GCTs (n=665, testis n=485, ovarian n=180) were more common than extragonadal GCTs (n=149). Stage distribution for testicular and extragonadal GCTs shifted between 1990 and 2004 and 2005–2018 towards more localized disease. The overall incidence remained stable over time, but a significant increase was noted for extragonadal GCTs in the 0–9 years age group. Survival of extragonadal GCTs (5-year OS 84.1%, 95% CI 77.1–89.1), in particular mediastinal GCTs (5-year OS 66.7%, 95% CI 45.7–81.1), was lower than that of gonadal GCTs (5-year OS testis 95.0%, 95% CI 92.7–96.7;ovary 97.8%, 95% CI 94.2–99.2). The 5-year OS of our entire cohort was 93.6% (95% CI 91.7–95.1). Five-year OS significantly increased from 89.5% (95% CI 86.1–92.2) in 1990–2004–97.4% (95% CI 95.3–98.5) in 2005–2018. Conclusions: Although the incidence of all malignant pediatric extracranial GCTs remained stable during 1990–2018, an increase was observed for extragonadal GCTs in younger children (0–9 years). There was a shift towards more localized disease for testicular and extragonadal GCTs. Five-year OS increased over time exceeding 90% (91.4%, 95% CI 82.7–95.8) in the most recent diagnostic period. Mediastinal GCTs had the lowest OS, supporting the need for future research.