GCT-63. STEREOTACTIC RADIOSURGERY FOR RESIDUAL LESIONS OF PINEAL NON-GERMINOMATOUS GERM CELL TUMORS AFTER CONVENTIONAL RADIOTHERAPY: A RETROSPECTIVE STUDY

OBJECTIVE: To explore the efficacy and safety of SRS for residual lesions of NGGCTs after conventional RT. METHODS: The clinical data of patients with iGCT who were admitted to Department of Oncology, Guangdong Sanjiu Brain Hospital between January 1, 2008 and December 30, 2019 were gathered. Those who were pathologically or clinically diagnosed with NGGCTs, with lesions located at pineal region, limited stage and residual lesions (with a maximum diameter>10mm) of pineal NGGCTs after RT with a total dose of 50-54Gy/25-30f, were eligible for the study. Several indexes such as local control rate, PFS, OS and treatment-related toxicity were analyzed. RESULTS: A total of 27 patients were included; all were male, with a median age of 16 years (range 8–31 years). The patients were followed-up to December 30, 2019, but there were 2 cases lost to follow-up. The median follow-up time was 34 months (range 8–142 months). After a month of treatment with SRS, the ORR and DCR were 71.4% and 95.2%, respectively. During follow-up, 5 cases had radiographic progressions, including 3 cases combined with increased AFP which were diagnosed with local recurrence and 2 cases diagnosed with GTS；The 3y-PFS and OS were 85.2% and 88.0%.no acute radiation response was found after treatment with SRS, and only one patient had brain neurotoxicity. CONCLUSION: SRS for residual lesions of NGGCTs after RT is proved to be safe and feasible, with well tolerance, which is beneficial for the improvement of local control and the prolongation of survival.