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: Recent studies have shown that hypofractionated simultaneous integrated boost-intensity-modulated radiation therapy (SIB-IMRT) provided certain survival benefits over other fractionation methods for high-grade gliomas. However, the best hypofractionation mode and its efficacy have not been confirmed. The purpose of this study was to investigate the maximum tolerated dose (MTD) of hypofractionated SIB-IMRT with stepwise escalating doses combined with temozolomide (TMZ) for treating malignant gliomas.

Methods: The patients received concurrent postoperative radiotherapy and chemotherapy. SIB-IMRT was adopted to increase the dose both in the surgical cavity and residual tumor (planning target volume 1). The dose at each fraction was gradually increased from 2.8 Gy/f (total of 20 times), with an escalating dose interval of 0.4 Gy. The planning target volume 2 involved the 2 cm region around surgical cavity, and residual tumor remained unchanged, with 2.5 Gy each time and a total of 50 Gy/20f. TMZ was administered with a dose of 75 mg/m/day during radiotherapy. Adjuvant TMZ was given at 150-200 mg/m/day for 5 days every 28 days. A total of 16 patients were enrolled.

Results: Three patients exhibited dose-limiting toxicity (DLT), two cases reported Grade 3 headache in the 3.6 Gy/f and 4 Gy/f dose groups, and one patient developed persistent seizures attacks in the 4 Gy/f dose group. Therefore, 4 Gy/f was considered the DLT and the lower dose level of 3.6 Gy/f was regarded as the MTD in the study, with tolerable adverse reactions. The median overall survival (OS) and median progression-free survival (PFS) in this study were 19 and 16 months, respectively. The 1- and 2-year OS and PFS were 86.7%, 31.0% and 73.7%, 26.7%, respectively.

Conclusions: It showed that the treatment of high-grade gliomas with hypofractionated SIB-IMRT combined with TMZ had an MTD of 3.6 Gy/f (72 Gy/20f). In addition, the results preliminarily showed improved survival.