P14.78 Comparison of progression-free survival after reirradiation of local and distant glioblastoma’s relapses

Abstract

Abstract BACKGROUND Despite using of modern comprehensive approaches to the treatment of patients with glioblastomas (GB) it invariably recur after a median interval of less than 7 months. Relapses are inevitable and is often the leading cause of death in patients. About 80–90% of recurrences are local, distant relapses are 5–20%. The optimal treatment strategy of recurrent GB have not yet been determined. MATERIAL AND METHODS The analysis included 130 patients with 160 lesions after primary combined treatment. Progression was assessed based on the RANO criteria. All patients have been re-irradiated in various regimens: 26 pts with median dose 60 Gy/30 fr, 20 pts with median dose 45 Gy/15 fr, 74 pts with dose 24-35Gy for 3–7 fr., 10 pts with median dose 22Gy/1fr. The scheme and regimen of fractionation were determined by tumor volume, localization and functional status of patient. Chemotherapy was changed to a regimen with Bevacizumab (BVZ) before the re-irradiation. According to the EORTC criteria lesions were divided as local (n=112) and distant (n=48) progression with median volume 23.6 cc and 14.7 cc respectively. RESULTS The median progression-free survival in the whole group was 8.2 months(95% CI 7–8.7). Progression-free survival at 6; 12 and 24 months was 65.8%; 21.9% and 4% respectively. Progression-free median survival after treatment of local and distant glioblastoma recurrences was different: 7.6 and 9.2 months, respectively (p = 0.048). In 17.4% radiation necrosis was detected according to MRI and 11C-methionine PET-CT data. Steroid and BVZ therapy were effective in these cases, no one of them was reoperated. CONCLUSION Re-irradiation for GB recurrences is effective and safe way for improvement of outcomes in patients with progression. In the group of patients with local relapses, local control is lower than in the group of distant ones. It may associated with the increasing of the radioresistance of tumor cells after the initial combined treatment. Further studies are needed to compare and assess the role of radiobiological and others factors in the development of local and distant recurrence.The research was supported financially by RFBR (Project No. 18-29-01061).