RONC-20. RECURRENT HIGH-GRADE ASTROBLASTOMA TREATED WITH STEREOTACTIC RADIOTHERAPY

INTRODUCTION: Astroblastoma is a rare, mostly supratentorial glial tumor, occurring predominantly in children and young adults. However, treatment strategies have not yet been established for this rare disease. CASE PRESENTATION: A 6-year-old male presented with headache and nausea. CT and MR imaging revealed a left frontal mass lesion with slight edema and macrocalcifications. Gross tumor resection was performed. Histological examination found neoplastic cells with astroblastic characteristics, and a striking perivascular array of pseudorosettes. The final diagnosis was high-grade astroblastoma. MR imaging 13 months after surgery suggested local recurrence and enlargement was found 3 months later. Stereotactic radiotherapy (SRT) was performed. MR imaging after SRT showed enhanced cyst formation around the tumor bed, suggesting tumor recurrence. However, (11)C-methionine PET revealed radiation necrosis. The last follow-up MR imaging 15 months after SRT showed no further recurrence. CONCLUSION: Astroblastoma is rare, so no optimal management is known. SRT may be effective to treat recurrent astroblastomas. (11)C-methionine PET/CT is useful for the differentiation from radiation necrosis.