ESTRO 2020 Abstract Book

S548 ESTRO 2020

had a brain progression (after 6 cycles). Two grade 2 hypothyrodism events (12° and 13° respectively) were registered. Nine patients began Durvalumab, 7 are still on going. Temporary discontinuation due to adverse events occurred in 3 patients (one G2 hyperthyroidism, two G2 pneumonitis and one G3 neutropenia). Permanent discontinuation occurred in 2 patients: one due to toxicity (G2 hypotiroidism associated with G2 hyposurrenalism) and one due to encefalic disease progression. Conclusion The new era of consolidation immunotherapy has changed the prospective of the radical CRT in unresectable, stage III, NSCLC. Durvalumab is the first immune checkpoint inhibitor to demonstrate a favorable impact on PFS and OS in this setting. Further investigations should show the possible interaction between immunotherapy and CRT. These preliminary results underline the role of PDL1 status as main limit to Durvalumab program recruiting. Longer follow up is necessary to better define the safety profile and to collect the real life data. PO-1029 Preliminary analysis of patient cohorts treated pre vs post approval of consolidation IO in LA- NSCLC J. Taugner 1 , L. Käsmann 1 , C. Eze 1 , O. Roengvoraphoj 1 , A. Tufman 2 , C. Belka 1 , F. Manapov 1 1 LMU University Hospital Grosshadern, Department of Radiation Oncology, München, Germany ; 2 LMU University Hospital Innenstadt, Department of Pneumology, München, Germany Purpose or Objective Chemoradiotherapy (CRT) followed by consolidation treatment with PD-L1 Inhibitor Durvalumab is the new standard of care for inoperable stage III NSCLC patients. Present study will chronologically compare survival in three inoperable stage III patient cohorts treated from 2011 to 2019 in our tertiary cancer centre. Material and Methods Retro- and prospectively collected data of patients treated with CRT with and without Durvalumab from three cohorts: (retrospective (re): 01.2011-12.2016; prospective (pro): 01.2017-10.2018 and prospective Durvalumab (ProDurva): 11.2018-present) were analyzed. Results In the re, pro and ProDurva cohorts, 99, 48 and 19 Patients have been treated with multimodal approach. The median follow up was 17.2, 23.2 and 6.9 months respectively. 18F- FDG-PET/CT for treatment planning was performed in 94%, 96% and 100% of patients in the re, pro and ProDurva corhort, respectively. All patients were irradiated to a total dose of at least 50Gy (median dose: 66Gy) in 3D- conformal, IMRT and /or VMAT technique. The absolute majority of patients (re: 60%; pro: 85 %; ProDurva: 94 %) received two cycles of concomitant platinum based chemotherapy. Across all treated patients we did not observe grade 4 or 5 non-hematological toxicity. Grade III pneumonitis was documented in 5/99 , 3/48 and 3/19 patients in the re, pro and ProDurva cohorts. Median OS was 20.8 months in the re and not reached in the pro and ProDurva cohorts. Six months after CRT end the PFS rates were 61% in the re, 65% in the pro and 80% in the ProDurva cohort (p=0.015), respectively. Rates of brain metastasis 6 months after completion of CRT in the re, pro and ProDurva cohort were 8,1%, 6,3% and 6,6%.

Conclusion Since 2011 we observe a significant improvement of PFS and OS in inoperable patients with stage III NSCLC after multimodal therapy. PFS rates of the ProDurva cohort are similar to published data (PACIFIC). PO-1030 Challenges on the CT follow-up after SBRT to early stage NSCLC A. Giraldo Marin 1 , M.M. Marti Laosa 1 , M. Ramos 1 , J. Giralt 1 1 Hospital Universitari Vall d`Hebron, Radiation Oncology, Barcelona, Spain Purpose or Objective SBRT has been increasingly used for the majority of non surgical patients with early-stage non-small cell lung cancer, as a result of high rates of local control (80–95%) reported from the literature The radiological changes observed after SBRT, during the follow-up, contrast from pts treated with conventional techniques, and sometimes lead us to an inadequate assessment of the radiological response. The aim of this study is to describe the incidence of the radiological changes and the presence of “high-risk features” (HRFs) on the follow-up in our pts. Material and Methods A retrospective review was conducted with the CT scans from patients (pts) treated between 2015 - January 2019 in our center. Patients were included in the analysis, if they had baseline imaging and control CT at <6, 12, 24 and 36 months (m). Patients without histological diagnosis or previous radiotherapy in thorax were not included. The follow-up finished, when the evidence of recurrence was confirmed. All pts underwent chest CT scan before SBRT and at 3, 6, 12, 18, 24m after, and then annually. Several previous studies, have identified CT-based HRFs in pts treated with SBRT. Acute and chronic CT changes were defined as those occurring within the first 5m and later (6- 11, 12-23, 24-35 and 36-47m) of the treatment, using a scoring system described previously in the literature. Each CT scan was evaluated and benign and HRFs were recorded after 6m (Fig1). Results A total of 60 lesions from 56 pts treated with SBRT for stage I-II NSCLC were assessed. The median age was 72 y (56-89), and the median duration of CT follow-up was 23.5 m (3–54 m). Out of these, we identified 60 images to evaluate acute changes and 39, 29 y 12 to evaluate changes at 12, 24 and 36m, respectively. In 53,3% of cases was no evidence of acute radiological changes (Fig1). Late parenchymal CT changes were seen for all lesions at some point during the follow-up period. The different patterns seen chronically changed during the follow-up (Fig2). Many lesions demonstrated a modified conventional pattern