Fractionated stereotactic radiosurgery with volumetric modulated arc therapy (Rapid Arc) for reradiation in recurrent high grade gliomas

Background: To evaluate 'Rapid Arc (RA)' technique for delivering fractionated stereotactic radiosurgery (FSRS) in patients with recurrent high grade gliomas (HGGs) for minimizing the dose to previously radiated high dose brain volume. Materials and Methods: Between April 2010 and February 2011, 16 consecutive patients with recurrent HGGs and previously treated with intensity modulated radiation therapy (IMRT) and Temozolamide received FSRS. The median time between IMRT and FSRS was 10.72 months. FSRS to a dose of 30 Gy in a median of 5 fractions was delivered to the recurrent tumor (gross tumor volume [GTV]). Brain volume around the GTV and previously treated to a mean dose >50 Gy was delineated as "Avoidance Volume (AV)." Patients were planned with both RA and Dynamic Conformal Arc (DCA) to achieve minimum dose to AV. Dose received by GTV, AV, rest of the normal brain (brain minus PTV) and conformity index (CI) and heterogenecity index (HI) were compared by the two techniques. Results: At a median follow up of 7.33 months, median progression free and overall survival was 6.4 and 9.3 months, respectively. Mean dose to AV was significantly lower with RA as compared with DCA (10.8 Gy vs. 15.5 Gy, P - 0.0001) with no significant difference in the dose delivered to GTV. No patient developed radiation necrosis. Conclusion: As compared with DCA, RA delivered significantly less dose to previously radiated high dose brain volume. It may contribute to minimizing the risk of radionecrosis with stereotactic radiosurgery (SRS) in patients with recurrent HGG.