Retrospective study of stage IV extracranial germ cell tumors: A report from the Japan Children's Cancer Group

Stage IV germ cell tumors (GCTs) have poor prognoses, and comprehensive data on these tumors in Japan are limited due to their rarity. This study aimed to assess the clinical characteristics, treatment outcomes, and prognostic factors of pediatric and adolescent patients with extracranial stage IV GCTs.

A retrospective survey was conducted among patients diagnosed before the age of 20 years between January 1, 2000 and December 31, 2019. Data were collected from 49 patients (30 males and 19 females) across 31 institutes.

The median age at diagnosis was 3.1 years (range 0.6-18.8 years). The most common pathological diagnosis was yolk sac tumor (YST). All patients received chemotherapy, and 40 underwent second-look surgery, including 5 of the 6 patients who had not undergone biopsy before chemotherapy. The 5-year overall survival and progression-free survival rates were 65.6% and 58.0%, respectively. In univariate analysis, age <11 years, YST or mixed-type GCTs (GCTs with YST), and attempted surgical resection were identified as favorable prognostic factors. In multivariate analysis, patients who underwent total resection at any point during treatment demonstrated significantly better outcomes.

In this Japanese cohort of patients aged <20 years with extracranial stage IV GCTs, age ≥11 years was confirmed as a poor prognostic factor, consistent with previously reported findings. Even for stage IV GCTs, the ability to achieve total or subtotal surgical resection was associated with long-term survival.