Treatment of High-grade Gliomas Using Escalating Doses of Hypofractionated Simultaneous Integrated Boost-intensity Modulated Radiation Therapy in Combination With Temozolomide - a Modified Phase I Clinical Trial

Background: Postoperative conventional radiation at 60 Gy/30f is currently still considered the standard radiotherapy mode for high-grade gliomas; however, the efficacy is still unsatisfactory. Studies in recent years have shown that hypofractionated simultaneous integrated boost-intensity modulated radiation therapy (SIB-IMRT) has certain survival benefits over other fractionation methods; but, the best hypofractionation mode and its efficacy have not been confirmed. The purpose of this study is to investigate the maximum tolerated dose (MTD) of hypofractionated SIB-IMRT with stepwise escalating of doses combined with temozolomide (TMZ) for the treatment of malignant gliomas. Methods: Malignant gliomas patients receive concurrent postoperative radiotherapy and chemotherapy. The simultaneous integrated boost-intensity modulated technology is adopted to increase both the dose in the surgical cavity and residual tumor (PTV1). The dose at each fraction is gradually increased from 2.8 Gy/f (total of 20 times) with an escalating dose interval of 0.4 Gy. The planning target volume (PTV2) including the 2cm region around surgical cavity and residual tumor remain unchanged, with 2.5 Gy each time and a total of 50 Gy/20f. The subsequent group of patients is advanced to the next dose level until dose-limiting toxicity (DLT) is present. The dose, one level lower than the DLT, is the MTD. The highest target single dose is 4 Gy/f. TMZ is administered orally every day at 75 mg/m2 during radiotherapy and at 150-200 mg/m2 for 12 cycles following completion of chemoradiotherapy.