Abstract BACKGROUND Non-germinomatous germ cell tumors (NGGCTs) require treatment involving combinations of chemotherapy, surgery, and radiotherapy. The radiotherapy field is typically focal in Europe and craniospinal in North America. Unlike germinomas, there are conflicting results for the effectiveness of ventricular field irradiation, and there is not enough data documenting the histology and tumor markers for tumors that relapse along the ventricles in patients who receive focal irradiation. METHODS We performed a literature review for English-language literature from 1998 to 2024 to to analyze the incidence, histopathology and tumor marker levels for NGGCT patients who initially received chemotherapy followed by focal radiotherapy and ended up having of ventricular relapses. RESULTS We identified 47 cases with relapsed NGGCT. However, only 8 cases were along the ventricles. Six of these were ventricular only, including two presumed germinomas based on tumor markers, three biopsy-proven germinomas, and only one case with bHCG levels exceeding ≥1000 IU/l. Two had combined relapses involving both the ventricular and spinal regions; one had pathology-proven germinoma but with elevated alpha-fetoprotein, and the other exhibited bHCG levels between 50 and 200 IU/l. CONCLUSION Ventricular relapses in NGGCT patients who receive focal radiotherapy should be investigated further. Whole ventricular radiotherapy may be required to prevent the relapse of germinoma elements. However, further information is essential before making any changes in the radiotherapy doses and fields.

GCT-09. VENTRICULAR RELAPSES OF INTRACRANIAL GERM CELL TUMORS FOLLOWING FOCAL RADIOTHERAPY