Hypofractionated radiotherapy with simultaneous integrated boost (SIB) plus temozolomide in good prognosis patients with glioblastoma: a multicenter phase II study by the Brain Study Group of the Italian Association of Radiation Oncology (AIRO)

Introduction: A multicenter phase II study for assessing the efficacy and the toxicity of hypofractionated radiotherapy with SIB plus temozolomide in patients with glioblastoma was carried out by the Brain Study Group of the Italian Association of Radiation Oncology. Methods: Twenty-four patients with newly diagnosed glioblastoma belonging to Recursive Partitioning Analysis classes III and IV were enrolled. The prescribed dose was 52.5 Gy in 15 fractions of 3.5 Gy and 67.5 in 15 fractions of 4.5 Gy to the SIB volume. Dose constraints for the hypofractionated schedule were provided. Radiotherapy was associated with concomitant and sequential temozolomide. Results: Median overall survival (OS) was 15.1 months, while median progression-free survival (PFS) was 8.6 months. Actuarial OS at 12 months was 65.6% ± 0.09, whereas actuarial PFS at 12 months was 41.2% ± 0.10. Status of methylation of MGMT promoter resulted to be a significant prognostic factor for OS. Radiotherapy-related acute toxicity was not relevant. Three patients (12.5%) had G3 myelotoxicity that required temozolomide temporary interruption or dose reduction during the chemotherapy. However, chemotherapy was not definitely discontinued for toxicity in any case. One patient out of 24 (4.2%) developed radionecrosis that required surgical resection with no evidence of disease in the surgical specimen. Conclusions: This trial confirms that hypofractionated radiotherapy with SIB and association with temozolomide may be a reasonable and feasible option for good prognosis patients with GBM.