ID #913 A Regional Survey of Central Nervous System Germ Cell Tumors in Kumamoto Prefecture, Japan: Long-Term Follow-Up Study

Introduction Central Nervous System Germ Cell Tumors (GCT) may offer prospects for long-term survival. While recent reports such as ACNS1123 and SIOP CNS GCT II exist, follow-up periods remain insufficient. We analyzed data from Kumamoto Prefecture, with follow-up periods extending up to 45 years. Methods We examined epidemiological characteristics, long-term treatment outcomes, and late effects in GCT cases from 1977 to 2025. Results A total of 112 cases were diagnosed with GCT over the 49-year period in Kumamoto prefecture, Japan. Comparing periods before chemotherapy was incorporated into treatment (1977-1987), when PE/ICE therapy was used (1988-2009), and when CARE/ICE therapy was used (2010-2025), an increasing trend in long-term survival cases was confirmed. For germinoma, the 5-year survival rate was 13 out of 19 cases (68.4%) in 1977-1987, 24 out of 30 cases (80%) in 1988-2009, and 19 out of 20 cases (95%) in 2010-2020. The most recent 2006-2015 germinoma cases also showed a 10-year survival rate exceeding 90%. Comparing recurrence rates between CARE (Carboplatin and Etoposide) and ICE (Ifosphamide, Cisplatin and Etoposide) in germinoma patients showed 23.1% for CARE and 8.7% for ICE. Regarding late effects, among GCT cases, 11 out of 57 patients (19.3%) surviving over 10 years developed radiation-induced tumors (6 meningiomas, 4 high-grade gliomas, 1 fibroma). The average time from initial GCT treatment to the development of radiation-induced tumors was 18.6 years [range: 9-24 years] for meningiomas and 14.3 years [range: 10-25 years] for high-grade gliomas, suggesting that at least 10 years of follow-up is insufficient. These complications of radiation-induced tumors occurred in cases with higher initial treatment doses of more than 50 gray in total radiation. Conclusion This study reconfirmed the increasing trend of long-term survivors among GCT patients. It underscores the importance of treatment selection considering late effects and the long-term follow-up more than 10 years is essential for truly evaluating the treatment outcomes for GCT.