Introduction: The authors analyzed the outcomes of boost stereotactic radiosurgery (SRS) for residual or recurrent GBM and evaluated factors that affected patient overall and progression free survival.
Methods: Over a 15 year period, we performed Gamma Knife® SRS in 297 patients with histologically proven GBM. Prior resection was considered as gross total in 68, subtotal in 133, and biopsy only in 96. The median patient age was 57 years (23-89 years) and the median tumor volume was 14 cc (0.26-84.2 cc). The median prescription dose delivered to the tumor margin was 15 Gy (9-25 Gy). The median follow-up time was 8.6 months (range, 1.1-173 months). Cox regression models were used to analyze survival outcomes. Variables examined included age, residual versus recurrent tumor, prior chemotherapy, time to first recurrence, SRS dose, and gross tumor volume (GTV).
Results: In this retrospective analysis the median patient survival after radiosurgery and after diagnosis was 8.9 and 17.7 months respectively. The 1-year and 2-year overall survivals (OAS) from SRS were 37.9% and 16.7% respectively. The 1-year and 2-year overall survivals (OAS) from diagnosis were 72.5% and 29.5% respectively. Multivariate analysis suggested that only younger age (p<0.001), higher KPS (p=0.045) and smaller tumor volume (less than 14cc: p<0.001) were significantly associated with increased OAS after SRS. In addition, the use of chemotherapy (0.04) was significantly associated with increased OAS from diagnosis. The extent of surgical resection (gross total, subtotal, or biopsy) had no effect on OAS in this series. Adverse radiation effects were seen in 69 patients (23%). Fifty-eight patients (19.5%) required repeat resection after SRS. A modified RPA classification was also used for survival analysis. In the present series the median survivals from diagnosis for class III, IV and V+VI were 31.6, 21.3, and 16.7 respectively.
Conclusions: In this experience almost 30% of GBM patients selected for adjuvant SRS had an overall survival of two years. Our data supports the role of adjuvant radiosurgery for selected patients with recurrent GBM.
Patient Care: Use of adjuvant Radiosurgery can improve overall survival in selected patients with Glioblastoma.
Learning Objectives: By the conclusion of this session, participants should be able to: 1) Describe the role of radiosurgery in the management of patients with recurrent glioblastoma, 2) Discuss, in small groups the indications of radiosurgery for GBM, 3) Identify the patients who can benefit from adjuvant radiosurgery for GBM.