Multi‐institutional analysis of treatment modalities in basal ganglia and thalamic germinoma

BACKGROUND: Central nervous system (CNS) germinomas are treatment-sensitive tumors with excellent survival outcomes. Current treatment strategies combine chemotherapy with radiotherapy (RT) in order to reduce the field and dose of RT. Germinomas originating in the basal ganglia/thalamus (BGTGs) have proven challenging to treat given their rarity and poorly defined imaging characteristics. Craniospinal (CSI), whole brain (WBI), whole ventricle (WVI), and focal RT have all been utilized; however, the best treatment strategy remains unclear. METHODS: Retrospective multi-institutional analysis has been conducted across 18 institutions in four countries. RESULTS: For 43 cases of non-metastatic BGTGs, the 5- and 10-year event-free survival (EFS) were 85.8% and 81.0%, respectively, while the 5- and 10-year overall survival (OS) were 100%, and 95.5%, respectively (one patient fatality from unrelated cause). Median RT doses were as follows: CSI: 2250 cGy/cGy(RBE) (1980 to 2400 cGy/cGy[RBE]), WBI: 2340 (1800 to 3000 cGy/cGy[RBE]), WVI: 2340 cGy/cGy(RBE) (1800 to 2550 cGy/cGy[RBE]), focal: 3600 cGy (3060 to 5400 cGy). Thirty-eight patients (90.5%) received chemotherapy. There was no statistically significant difference in the EFS based on initial field extent (p=0.84). Nevertheless, no relapses were reported in patients who received CSI or WBI. Chemotherapy alone had significantly inferior EFS compared to combined therapy (p=0.0092), but patients were salvageable with RT. CONCLUSION: Patients with BGTGs have excellent outcomes and RT proved to be an integral component of the treatment plan. This group of patients should be included in future prospective clinical trials and the best RT field should be investigated further.