Phase II Trial of Pathology-based Tripartite Treatment Stratification for Patients with CNS Germ Cell Tumors: A Long-term Follow-up Study.

Background: A previous Phase II clinical trial, conducted from 1995 to 2003, evaluated CNS germ cell tumors (GCTs) using a three-group treatment stratification based on histopathology. The primary objective of the study was to assess the long-term efficacy of standardized treatment regimens, while the secondary objective focused on identifying associated long-term complications.

Methods: Total 228 patients were classified into three groups for treatment: germinoma (n=161), intermediate prognosis (n=38), and poor prognosis (n=28), excluding one mature teratoma case. Treatment involved stratified chemotherapy regimens and varied radiation doses/coverage. Clinical data was retrospectively analyzed at a median follow-up of 18.5 years.

Results: The treatment outcomes for germinoma, with or without syncytiotrophoblastic giant cell, were similar. The 10- and 20-year event-free survival rates for the germinoma, intermediate, and poor prognosis groups were 82/76/49% and 73/66/49%, respectively. Overall survival (OS) rates were 97/87/61% at 10 years and 92/70/53% at 20 years. Germinomas in the basal ganglia, treated without whole-brain radiation therapy (WBRT), frequently relapsed but were effectively managed with subsequent WBRT. Deaths in germinoma cases had varied causes, whereas deaths in the poor prognosis group were predominantly disease-related. Nineteen treatment-related complications were identified in 16 patients, with cumulative event rates of 1.9% at 10 years and 11.3% at 20 years. OS rates at 1 and 2 years post-relapse for tumors initially classified as germinoma, intermediate, and poor prognosis were 94/88/18% and 91/50/9%, respectively.

Conclusions: Initial treatment intensity is crucial for managing non-germinomatous GCTs, while long-term follow-up for relapse and complications is imperative in germinomas. Irradiation extending beyond the immediate tumor site is essential for basal ganglia germinomas. Addressing relapse in non-germinomatous GCT remains a significant challenge.