RTHP-28. REPEAT SALVAGE GAMMA KNIFE RADIOSURGERY FOR RECURRENT GLIOBLASTOMA

Abstract

BACKGROUND: Our institutional practice has been to treat recurrent glioblastoma (GB) with gamma knife radiosurgery (GK). We evaluated survival outcomes in these patients. METHOD(S): This was a single institution review of patients with GB who underwent a definitive course of postoperative external beam radiotherapy (EBRT) with concurrent chemotherapy and subsequently treated with GK for recurrence or progression between 2006 and 2017. Overall survival (OS) was determined using Kaplan-Meier statistics. RESULT(S): 87 patients were identified with median age of 55 years. Median follow-up was 21.1 months. The majority of patients underwent gross total (57%) or subtotal resection (38%). 23 (26%) underwent surgery for recurrence. The median marginal dose for first GK was 17 Gy and 14 Gy for patients with 1 target or >1 target, respectively. 4 patients underwent fractionated GK treatment with 18-25 Gy in 3-5 fractions. 20 patients underwent a second GK treatment and 1 patient was treated three times. Time from first to second GK was 6 months, with a median marginal dose for second or third GK of 15 Gy. 10 patients underwent a second course of EBRT ranging from 30-59.4 Gy in 10-33 fractions; 2 patients received stereotactic body radiation therapy with 25 Gy in 5 fractions. Median OS was 21.4 months. 2- and 5-year OS was 41.8% and 9.9%, respectively. Median survival after first and second GK was 9.6 months and 4.7 months, respectively. There was a trend towards improved OS for patients treated with both EBRT and GK compared to GK alone (Median OS: 2.85 years vs 1.75 years, p=0.14). DISCUSSION(S): To our knowledge, this study reports on the largest cohort of patients treated with salvage GK for recurrent GB. The survival outcomes compare favorably to contemporary trials. Future studies will include an analysis of toxicity and patterns of failure.