ESTRO 2020 Abstract book

S526 ESTRO 2020

Purpose or Objective Brain metastases (BMs) have poor prognosis, therefore identifying subgroups of patients’ candidates to aggressive therapy might improve survival. Prognostic indices such as disease-specific graded prognostic assessment (DS-GPA) are used to select patients´ candidates for radiosurgery (SRS). Non-Small cell lung cancer (NSCLC) DS-GPA doesn´t consider primary tumor (PT) status. The aim of this study was to analyze if there are differences in overall survival (OS) after SRS between patients with controlled PT that develop BMs (Group 1) and newly diagnosed NSCLC with synchronous BMs (Group 2). The secondary objective was validating DS-GPA in this population. Material and Methods Retrospective analysis of 82 NSCLC patients with BMs´ undergoing SRS at our center between 2011 and 2018 (47 in group 1 and 35 in group 2). Patients were stratified according to NSCLC DS-GPA to evaluate the accuracy of survival estimates. Results Median OS was 17 months for group 1 (95% CI 5.7-28.3) and 12 for group 2 (95% CI 1-22.9), with no statistically significant differences between groups (p=0.654).In multivariate analysis, Karnofsky performance-status (p=0.005) and BMs´ surgery (p=0.005) were significant predictors of OS. Median OS stratified according to DS-GPA for scores 1.5, 2.5-3, and 3.5-4 were 12, 21, 51 months, respectively (p=0.028). No differences were observed between both groups´ regarding OS. According to our results median OS stratified according to DS-GPA was consistent with OS reported in previous studies.

PO-0899 Risk of brain Radionecrosis after radiosurgery in oligometastatic patients I. Chiovatero 1 , C. Mantovani 1 , G.C. Iorio 1 , C. Cavallin 1 , A. Vella 1 , E. Orlandi 1 , M. Cerrato 1 , S. Badellino 1 , D. Caivano 1 , M. Levis 1 , V. De Luca 1 , U. Ricardi 1 1 University of Turin, Department of Oncology, Torino, Italy Purpose or Objective To evaluate the toxicity profile of radiosurgery (SRS) focusing mainly on radionecrosis (RN) and to investigate for any clinical and dosimetric related factor in a cohort of oligometastatic brain patients. Material and Methods We retrospectively analysed the data of 75 oligometastatic patients (41 male, 34 female) with 129 lesions, treated at our Institution between 2015 and 2017. The average age at diagnosis was 64 years old. Most lesions were supratentorial (107/129), with an average volume of 3.5 cc. The primary tumor was lung cancer in 46 patients, breast cancer in 8 patients, colon-rectum cancer in 5 patients and miscellaneous in the remaining patients (16). Three patients received whole brain irradiation before SRS. In two cases a reirradiation was performed (at a median distance of 18 months after previous treatment). SRS was performed in 115 lesions with a median prescription dose (at the 80% isodose) of 21 Gy (range 16- 24 Gy), while a hypofractionated sterotactic treatment was performed in 14 lesions (24-27 Gy in three fractions in 12 lesions and 30 Gy in five fractions in two lesions). For each lesion, variables recorded included volume of brain receiving a specific dose (V5 Gy, V10 Gy, V12 Gy, V18 Gy), location/magnitude of hot spots, PTV volume, steroid therapy before treatment, concomitant systemic therapy (including immunotherapy or TKI). All patients underwent neuroradiological examination with brain MRI every three months; MRI spectroscopy and MRI perfusion were used to define a RN. RN was recorded using CTCAE scale (version 4.1). Results With a median follow-up after SRS of 12 months for surviving patients, the 1-yr local control was 82%. Twenty- seven patients showed RN on 31 treated metastases. RN was diagnoses on the basis of radiological features in 24 patients and in remaining three patients with histological confirmation. RN was scored as grade I in 15 lesions, grade II in three lesions, grade III in 13 lesions. Univariate analysis showed V5 Gy >18 cc (p 0.04), V10 Gy > 6 cc (p 0.03), median prescription dose (<18 Gy; p 0,006) and median PTV (median volume 1 cc; p 0.03) as indipendent risk factors for RN, while V12 > 4 Gy was marginally correlated with an higher risk of RN (p = 0.06). All dosimetric factors were strongly correlated, with a risk of RN of 38% for V5 Gy>18 cc, V12 Gy >4 cc, and V10Gy >6 cc. On multivariate analysis V10Gy and V12 Gy were significantly related to RN (p < 0.01). Conclusion SRS represents a feasible and effective treatment option for patients with brain metastases. A significant subset of patients may develop cerebral RN, which may eventually impact their quality of life. Dosimetric parameters of the healthy brain tissue (V5Gy, V12 Gy and V10 Gy) are strong predictors of the risk of RN and should thus be integrated in the planning process.In fact, a careful evaluation of these parameters is mandatory to limit the risk of RN and to prevent SRS- related complications.

Conclusion There are not differences in overall survival between NSCLC patients with BMs whether the primary tumor is controlled or if it has not yet received specific treatment.