P17.09.B REIRRADIATION AS A SALVAGE THERAPY FOR LOCAL GLIOBLASTOMA RECURRENCE

Abstract

Abstract BACKGROUND There is a lack of successful strategies to treat glioblastoma (GB) recurrences. Reirradiation is one of them, but it only can be considered in a few patients with localized relapses. This review aims to analyse the role of reirradiation in this setting and the management difficulties associated with this strategy. MATERIAL AND METHODS We have retrospectively reviewed the outcome of GB patients treated with surgery and the standard Stupp regimen, that have received stereotactic radiotherapy (RT) at the time of a local in-field relapse in our centre, during the period from 2005 to 2022. RESULTS 44 patients have been identified. The recurrence occurred at a median time of 9.7 months (m) after the end of the first RT. It was the first relapse in 89% of patients, and RT was given exclusively in 47.7% of cases. In the remaining patients, RT was combined with other treatments. The median maximum diameter of the relapse was 13.5 mm. Treatment schemes were mainly two: 35 Gy in 3.5 Gy daily fractions (52%) and 20 Gy in 5 Gy daily fractions (39%). Acute toxicity was mild, with worsening of previous neurological symptoms in only 15% of patients. After a median follow-up of 15 m, radiological responses were observed in 40% of patients, with a remarkable number of distant progressions in less than 6m (32.5%). The median time to progression was 4.8 m, being longer for patients treated at first relapse, females and with a Karnofsky index (KI) >70. The diameter of the relapse showed a tendency to impact in time to progression, but no differences for RT dose, RT scheme or type of strategy (exclusive RT vs combined) have been detected. The median overall survival after reirradiation was 14.9 m. Related prognostic factors were KI >70, size of the relapse (maximum diameter <25 mm) and reirradiation given at first relapse. Radiological changes after reirradiation were commonly observed (47% of patients); differentiating them from true local progression was often difficult. CONCLUSION Reirradiation is a feasible and safe therapeutic option to treat localized GB relapses, able to control the disease for a few months in selected patients, especially those with first recurrences and small lesions. Further studies must be performed to improve the radiological evaluation in these patients and to determine the optimal combination with other treatment modalities.