RONC-13. RADIATION INDUCED BRAIN STEM GLIOMA AFTER RADIATION THERAPY FOR MIXED GERM CELL TUMOR

We report a case of radiation-induced glioma in the pons after radiation therapy for germ cell tumor. A 17-year-old man was diagnosed as HCG and AFP secreting germ cell tumor at the age of 9. The tumor was located in the suprasellar region, which filled up most part of the third ventricle. Five courses of chemotherapy with cisplatin, etoposide, and cyclophosphamide, and whole ventricle plus local radiation therapy (total 51.2 Gy / 32Fr) were performed. After the treatment, most part of the tumor was regressed, and only small enhanced lesion remained. Six years after the treatment, he started to be ataxic, and worsened. An MRI revealed an enhanced lesion in the pons. Lesion biopsy was performed via the right cerebellar peduncle. Histopathological diagnosis confirmed the lesion was high grade glioma. He underwent extended local radiation therapy (50.4 Gy / 28 Fr) and administered temozolomide. Later, bevacizumab was added, and 3 months after treatment started, the size of the tumor was reduced and his symptoms were improving. There is no established treatment for radiation induced glioma. However, additional radiation therapy, temozolomide and bevacizumab appears to be useful to reduce tumor size and resolve the symptoms, even if it is transient.