ESTRO 2020 Abstract Book

S469 ESTRO 2020

proportional hazards regression modeling was used to assess associations between the BED and the outcome of death caused by lung cancer, adjusted for significant clinical covariates (p<0.05). The IBM SPSS v.25 software was used for statistical analysis. Results Patient, tumour and treatment characteristics are listed on Table 1. The median age was 64 years. The predominant stage was IVA (n =103). Performance status (ECOG-PS) 0-1 were predominant. The number of treated brain metastases were 1 (n=38), 2 (n=27), 3 (n= 19) and ≥4 (n=30). The median BED 10 was 39 Gy and 90 patients (78.9%) had died by cancer disease. The median follow-up time was 8,2 months (0,56-62,9 months). Cox analysis significant covariates identified were stage (IVA vs IVB), ECOG-PS (0-1 vs 2-3) and immunotherapy treatment. Higher stage and ECOG-PS were associated with increased likelihood of lung-cancer death and the opposite was seen for immunotherapy. The 83 patients receiving >30Gy BED 10 had a median survival of 5.4 months (95% CI 3.9-6.9), whereas the 31 patients receiving ≤30 Gy BED 10 had a median survival of 3.6 months (95% CI 2.6-4.5), p = 0.501. Stratified age group analysis showed a trend (p>0.05) to greater benefit for patients under 70 years old receiving whole-brain radiotherapy >30Gy BED 10 .

Conclusion In our brain metastatic lung cancer cohort, we found that biologically effective dose radiation therapy>30Gy BED 10 may improve survival and with a greater benefit for patients aged under 70 years old. PO-0874 Development of a prognostic model for patients with high-grade meningioma - the ELSA study K. Kessel 1,2 , W. Weber 3 , C. Zimmer 4 , B. Meyer 5 , S.E. Combs 1,2 1 Klinikum rechts der Isar- Technical University of Munich TUM, Department of Radiation Oncology, München, Germany ; 2 Institute of Radiation Medicine IRM, Helmholtz Zentrum München, Neuherberg, Germany ; 3 Klinikum rechts der Isar- Technical University of Munich TUM, Department of Nuclear Medicine, München, Germany ; 4 Klinikum rechts der Isar- Technical University of Munich TUM, Department of Neuroradiology, München, Germany ; 5 Klinikum rechts der Isar- Technical University of Munich TUM, Department of Neurosurgery, München, Germany Purpose or Objective To date, the treatment concepts and thus, outcome analysis for high-grade meningiomas are a challenge. It is a relatively rare disease, and in most centers, adjuvant radiotherapy (RT) after resection is the standard therapy, but remains controversial, especially in WHO grade II cases. Patients achieve a 5-year progression-free survival (PFS) of 30% - 60%, depending on the treatment concept. The ELSA study aims to evaluate outcomes after RT. Prognostic factors will be analyzed to create a recurrence prediction and prognosis model. Material and Methods We report first results on an ongoing evaluation based on 63 patients (WHO II or III) treated between 1996 and 2018. All patients were resected and received adjuvant, fractionated stereotactic RT with a median dose of 59.4