ESTRO 2020 Abstract Book

S482 ESTRO 2020

Of the RN that appeared among patients treated with MF- SRS, 100% were symptomatic while patients treated with SF-SRS 40% were symptomatic and 60% asymptomatic. Treatment of RN was Bevacizumab in 63%, Bevacizumab + corticosteroids in 7%, corticosteroids in 10% and surgery in 3%. 17% patients did not receive treatment. As for the patients who received bevacizumab, 42% received 6 cycles, 5% 5 cycles and 21% 4 cycles. 16% received less than 4 and another 16% more than 6 cycles. At 4 months 26% of patients treated with Bevacizumab had lesion reduction and 42% stable disease. 32% remaining lost follow-up. There was no relation between the number of bevacizumab cycles and radiological response at 4 months (p = 0.26). Conclusion RN is the most significant complication in patients treated with brain stereotactic radiotherapy. The incidence of RN is higher in patients treated with SF- SRS, however it is more frequently symptomatic in patients treated with MF-SRS. This can be explained by the greater field irradiated in these patients since the size of the lesions is usually larger. Bevacizumab is a treatment option for these patients. PO-0901 Stereotactic radiotherapy in brain metastases. Survival and radiological behavior analysis. S. Fernandez Alonso 1 , S.G. Guardado Gonzáles 1 , G. Pozo Rodríguez 2 , D. Lora Pablos 3 , J.F. Pérez-Regadera Gómez 1 1 Hospital Universitario 12 de octubre, Radiation Oncology, Madrid, Spain ; 2 Hospital Universitario 12 de octubre, Radiophysics, Madrid, Spain ; 3 Hospital Universitario 12 de octubre, Statistics, Madrid, Spain Purpose or Objective To compare the characteristics, survival and radiological behavior among patients with 1-3 brain metastases treated by single-fraction radiosurgery (SF-SRS) or multi-fraction radiosurgery (MF-SRS) in our center. Material and Methods 163 patients were treated between January/2011 and June/2018 and were retrospectively studied. Results 40% patients were men and 60% women. Mean age was 56 years. There were no differences in age, sex, Karnofsky performance status, size of lesion, previous local or systemic treatment. Histological diagnosis was lung adenocarcinoma EGFR naive (23%), other lung carcinoma (19%), triple negative breast (10%), melanoma (9%) and other histologies (39%). At the date of onset of brain metastases, 66% patients had the primary tumor controlled. According to RPA classification 49% was I, 50% II and 1% III. 68% cases presented a single lesion, 19% 2 lesions, and 13% 3 or more lesions; 65% were supratentorial, 14% infratentorial and 21% had involvement of both locations. A single lesion was treated in 83% cases, 2 in 12%, 3 in 4% and in 4 in 1%. 51% patients had received previous cranial treatment; 65% whole brain radiotherapy (WBRT), 25% surgery and 10% surgery + WBRT. 75% had received systemic treatment; 49% QT, 22% QT + immunotherapy, 15% exclusive immunotherapy, 9% QT + hormone therapy and 5% other treatments. 63% patients received MF-SRS (58% 7x500 cGy, 29% 6x500 cGy and 13% another fractionation). 42% patients received SF-SRS (95% 15 Gy, 3% 18 Gy and 2% another dose). 95% finished radiotherapy treatment. 62% received systemic treatment in the first month after

One-year survival of group treated with MF-SRS was 93% and of SF-SRS group 90%. Five-year survival was 53% and 59% respectively ( p =0.88). 42% progressed locally and 22% failure remote; of them, 49% had received MF-SRS and 51% SF-SRS ( p =0.58). Median time to local failure was one year and until remote failure three years. One and five-years survival of patients with progression were 81% and 49% in MF-SRS group and 79% and 51% in SF- SRS group ( p =0.95). Regarding radiological behavior at 3 months, 5% presented complete response (CR), 28% partial response (PR), 47% stable disease (EE) and 20% progression (PD). At 6 months, 11% had CR, 47% PR, 25% EE and 17% PD. At one year 17% had CR, 38% PR, 20% EE and 25% PD. At the end of the study 47% patients had died, 25% remain alive without disease, 12% are alive with extracranial disease, 7% with exclusive intracranial disease, 3% with intracranial and extracranial disease and 6% are unknown. Cause of death was systemic in 46%, cerebral in 37% and 17% foreign to tumor cause. Conclusion SF-SRS and MF-SRS are an effective treatment in brain metastases. There are no differences between SF-SRS y MF-SRS in survival and local control. The greatest evidence of radiological changes is from the sixth month after irradiation. PO-0902 Prognostic value of SVZ involvement in relation to tumor volume defined by MRI and FET PET in GBM M. Harat 1 , B. Małkowski 2 , R. Makarewicz 1 1 Collegium Medicum Nicolaus Copernicus University, Oncology and Brachytherapy, Bydgoszcz, Poland ; 2 Franciszek Lukaszyk Memorial Oncology Center, Nuclear Medicine, Bydgoszcz, Poland Purpose or Objective Subventricular zone (SVZ) involvement is associated with a dismal prognosis in patients with glioblastoma multiforme (GBM). Dual-time point (dtp) O-(2-[ 18 F]fluoroethyl)-L- tyrosine (FET) PET/CT (PET) may be a time- and cost- effective alternative to dynamic FET PET, but its prognostic value, particularly with respect to SVZ involvement, is unknown. Material and Methods Thirty-five patients had two scans 5-15 and 50-60 minutes after i.v. FET injection to define tumor volumes and SVZ involvement before starting radiotherapy. Associations between clinical progression markers, MRI- and dtp FET PET-based tumor volumes, or SVZ involvement and progression-free (PFS) and overall survival (OS) were assessed in univariable and multivariable analyses. Results The extent of resection was not related to outcomes. Albeit non-significant, dtp FET PET detected more SVZ infiltration than MRI (60% vs. 51%, p=0.25) and was significantly associated with poor survival (p<0.03), but PET-T1-Gad volumes were larger in this group (p<0.002). Survival was shorter in patients with larger MRI tumor volumes, larger PET tumor volumes, and worse Karnofsky performance status (KPS), with fused PET-T1-Gad and KPS significant in multivariable analysis (p<0.03). Uptake kinetics was not associated with treatment outcomes. Conclusion FET PET-based tumor volumes may be useful for predicting the worse prognosis of glioblastoma. The independent value of dtp FET PET parameters and SVZ infiltration as prognostic markers pre-irradiation has not been confirmed. Additionally the presence of SVZ infiltration is linked to higher PET/MRI-based tumor volumes.

RT; 40% QT and 60% other treatments. Median overall survival was 3.28 years.