ESTRO 2020 Abstract book

S577 ESTRO 2020

comorbidities. We studied toxicity and early mortality in stage III NSCLC in patients who were treated at a single institution in accordance with the 2014 ESMO guidelines. Material and Methods Details of all stage III NSCLC patients who underwent radical thoracic radiation to 50 Gy or higher between 2015- 2017 at our institution, were accessed from an ethics- approved database. Patients undergoing any surgery, SABR or who had previous thorax radiotherapy were excluded. Information on patient comorbidities, tumor and treatment characteristics, the incidence and severity of early toxicity, and dates of death were collected. Results A total of 129 patients with stage III NSCLC who were discussed at the joint multidisciplinary tumor board of our institution and referring hospitals fulfilled our inclusion criteria. Of these, 49.6% underwent cCRT with platinum- doublet chemotherapy, 34.1% sequential chemo- radiotherapy (sCRT) and 16.2% radiotherapy (RT) alone. In 14% of patients initially considered suitable for cCRT, the final treatment choice was sCRT (n=14) or only RT (n=4), for reasons ranging from poor performance (50.0%), patient preference (27.8%) or a large target volume (16.7%). Radiotherapy was delivered using hybrid or full Intensity Modulated Radiotherapy / Volumetric Modulated Arc Therapy. The prescribed dose was between 60-66 Gy in 89% of patients. Patient demographics, comorbidities, tumor and treatment characteristics, toxicity, and mortality rates are summarized below [Table]. Rates of ≥grade 3 toxicity for all 129 patients were as follows: esophagitis 14.0%, radiation pneumonitis 3.1% and other toxicities 4.7%. 90-day mortality rates for the cCRT, sCRT and RT arms were 1.6, 11.4 and 19.0%, respectively. The corresponding 1-year mortality rates were 21.9, 36.4, and 47.6%. Of all 90-day deaths, 60% were attributed to co- morbidities and 40% were considered lung cancer-related. Patient deaths observed between days 91-365 post- treatment were considered secondary to disease progression in 63.3%, and to co-morbidities in another 10%.

hazard ratio of 0.29 (CI: 0.14 - 0.58, p<10^{−3}) when adjusted for other clinical factors.

Conclusion In standard-of-care lung CyberKnife treatments, dose distributions that aid distant control are achieved 95% of the time. Although similar doses could be physically achieved by coplanar deliveries, current prescription practices result in worse DM outcomes for 25% of conventional lung SBRT patients. Our study suggests that adding an additional prescription parameter to a 30 mm shell outside the PTV could reduce distant recurrence rates in conventional SBRT patients. PO-0996 Early mortality in stage III NSCLC after radical non-surgical therapy following ESMO guidelines M. Ronden-Kianoush 1 , I.F. Remmerts de Vries 1 , I. Bahce 2 , P.F. De Haan 1 , M.A. Tiemessen 3 , F.O.B. Spoelstra 1 , V.D.M. Van Diepen 4 , C.J.A. Haasbeek 1 , S. Tarasevych 5 , H.J.M.A. Daniels 2 , M.R. Dahele 1 , S.M. Hashemi 2 , A. Becker 2 , J.D. Veltman 6 , L.M.M. Crombag 6 , S. Senan 1 , W.F.A.R. Verbakel 1 1 Amsterdam UMC - VUmc, Radiation Oncology, Amsterdam, The Netherlands ; 2 Amsterdam UMC - VUmc, Pulmonary Diseases, Amsterdam, The Netherlands ; 3 Dijklander Ziekenhuis Hoorn, Pulmonary Diseases, Hoorn, The Netherlands ; 4 Dijklander Ziekenhuis Purmerend, Pulmonary Diseases, Purmerend, The Netherlands ; 5 Zaans Medisch Centrum, Pulmonary Diseases, Zaandam, The Netherlands ; 6 Amsterdam UMC - AMC, Pulmonary Diseases, Amsterdam, The Netherlands Purpose or Objective The most recent European Society for Medical Oncology (ESMO) guideline recommends immunotherapy consolidation treatment using durvalumab for 12 months after completion of cCRT [ in press , Ann Oncol 2019]. Population studies of patients with stage III NSCLC report that only 20-50% of patients undergo cCRT, mainly due to concerns about toxicity in elderly patients with

Conclusion In patients with stage III NSCLC, the observed rates of acute toxicity of cCRT were similar to those reported in phase III trials, thereby allowing patients to be eligible for adjuvant durvalumab. High 90-day and 1-year mortality rates were observed in patients considered unsuitable for cCRT. Our findings seem to reflect the selection process that directs patients to the most appropriate treatment. More effort is required to identify key determinants of frailty in this population and to identify or develop the most suitable alternative strategies for those who are unfit for cCRT. PO-0997 Evaluation of outcome and toxicity of Durvalumab treatment after CRT in inoperable stage III NSCLC L. Käsmann 1 , J. Taugner 1 , C. Eze 1 , O. Roengvoraphoj 1 , C. Belka 1 , F. Manapov 1 1 LMU University Hospital Grosshadern, Department of Radiation Oncology, Munich, Germany