Fractionated stereotactic radiosurgery with concurrent temozolomide chemotherapy for locally recurrent glioblastoma multiforme: a prospective cohort study

Jeffrey Noah Greenspoon,1 Waseem Sharieff,1 Holger Hirte,1 Andrew Overholt,1 Rocco Devillers,2 Thorsteinn Gunnarsson,2 Anthony Whitton11Department of Oncology, McMaster University, ON, Canada; 2Department of Surgery, McMaster University, ON, CanadaAbstract: Local recurrence represents a significant challenge in the management of patients with glioblastoma multiforme. Salvage treatment options are limited by lack of clinical efficacy. Recent studies have demonstrated a significant response rate and acceptable toxicity with the use of fractionated stereotactic radiosurgery in this patient population. Our primary objective was to determine the efficacy and toxicity of fractionated stereotactic radiosurgery combined with concurrent temozolomide chemotherapy as a salvage treatment for recurrent glioblastoma multiforme. We prospectively collected treatment and outcome data for patients having fractionated stereotactic radiosurgery for locally recurrent glioblastoma multiforme after radical radiotherapy. Eligible patients had a maximum recurrence diameter of 60 mm without causing significant mass effect. The gross tumor volume was defined as the enhancing lesion on an enhanced fine-slice T1 (spin–lattice) magnetic resonance imaging, and a circumferential setup margin of 1 mm was used to define the planning target volume. All patients were treated using robotic radiosurgery with three dose/fractionation schedules ranging from 25 to 35 Gy in five fractions, depending on the maximum tumor diameter. Concurrent temozolomide 75 mg/m2 was prescribed to all patients. Tumor response was judged using the Macdonald criteria, and toxicity was assessed using the CTCAE (Common Terminology Criteria for Adverse Events). A total of 31 patients were enrolled in this study. The median overall survival was 9 months, and progression-free survival was 7 months. The 6-month progression-free survival was 60% with a 95% confidence interval of 43%–77%. The a priori stratification factor of small tumor diameter was shown to predict overall survival, while time to recurrence was not predictive of progression-free or overall survival. Three patients experienced grade 3 acute toxicity that responded to increased steroid dosing. One patient experienced a grade 4 acute toxicity that did not respond to increased steroids but did respond to anti-angiogenic therapy. Fractionated stereotactic radiosurgery with concurrent temozolomide has shown good short-term clinical and radiologic control with manageable acute toxicity. This regimen appears to provide superior efficacy to either temozolomide or fractionated radiosurgery alone. The results of this study support the continued evaluation of this regimen.Keywords: GBM, re-treatment, brain tumor, anti-angiogenic therap