ESTRO 2020 Abstract book

S592 ESTRO 2020

33% sequential therapy and 15% received no systemic therapy. The median OS was 17 months (95% CI; 14-20 months) and the median PFS was 9 months (95% CI; 8-11 months). The 1-, 2-, 3-, and 5-year OS and PFS were respectively; 55%, 31%, 21%, 6% and 34%, 16%, 12%, 4%. On multivariate analysis weight loss (HR 1.40, p=0.012), M- stage (HR 1.79, p=0.008) and lateralization of the primary tumor (HR 1.80, p=0.003) remained significantly associated with OS. The c-statistic for this model (corrected for optimism) was 0.63. M-stage (HR 2.22, p<0.001) and lateralization of the primary tumor (HR 1.48, p=0.031) remained significantly associated with PFS. The C-statistic for this model (corrected for optimism) was 0.65. In table 1 we calculated the negative predictive value for low-risk patients at 1 and 2 years OS/PFS. Percentage * Negative predictive value (NPV)** 95% Confidence interval (CI)*** 1 year OS 62.2 75.8 63.7-85.8 2 years OS 36.0 54.1 40.9-66.9 1 year PFS 38.2 47.9 35.9-60.1 2 years PFS 18.9 25.0 15.3-37.0 *OS and PFS in percentage for all included patients that had no missing data. **NPV for low-risk patients based on significant prognostic factors from the multivariate analysis ***CI for the NPV Conclusion M-stage and lateralization of the primary tumor are prognostic factors for OS and PFS. Weight loss is also a prognostic factor for OS. Both models need further improvement to create a tool for better patient selection. PO-1026 Role of neoadjuvant radiochemotherapy in non-Pancoast T4 N0/1 M0 NSCLC N. Guberina 1 , C. Pöttgen 1 , M. Schulter 2 , M. Guberina 1 , M. Stuschke 3 , G. Stamatis 4 , T. Plönes 4 , D. Theegarten 5 , T. Gauler 1 , K. Darwiche 6 , C. Aigner 7 , W. Eberhardt 8 1 Department of Radiotherapy- West German Cancer Center- University Hospital Essen- Germany, Department of Radiotherapy- West German Cancer Center- University Hospital Essen- Germany, Essen, Germany ; 2 Department of Oncology- West German Cancer Center- University Hospital Essen- Germany- Division of Thoracic Oncology- University Medicine Essen – Ruhrlandklinik- German Cancer Consortium DKTK- Partner Site University Hospital Essen- Germany, Departmen, ; 3 Department of Radiotherapy- West German Cancer Center- University Hospital Essen- Germany- German Cancer Consortium DKTK- Partner Site University Hospital Essen- Germany, Department of Radiotherapy- West German Cancer Center- University Hospital Essen-, ; 4 Department of Thoracic Surgery and Endoscopy- Ruhrlandklinik- West German Lung Transplantation Center- University Hospital Essen- Germany, Department of Thoracic Surgery and Endoscopy- Ruhrlandklinik- West German Lung Transplantation Center- University, ; 5 Institute of Pathology- University Hospital Essen- Germany, Institute of Pathology- University Hospital Essen- Germany, Essen, Germany ; 6 Department of Pulmonary Medicine- Section of Interventional Pneumology- Ruhrlandklinik- West German Lung Transplantation Center- University Hospital Essen- Germany, Department of Pulmonary Medicine- Section of Interventional Pneumology- Ruhrlandklinik-, ; 7 Department of Thoracic Surgery and Endoscopy- Ruhrlandklinik- West German Lung Transplantation Center- University Hospital Essen- Germany- German Cancer Consortium DKTK- Partner Site University

Gy; for OAR: EQD2=76 Gy) to the PTV. A GTV to CTV margin of 5 mm was used. PTV-margins were individually calculated based on the 4D-CT scan. Daily CBCT was performed for tumor match. Toxicities were reported using the CTCAEv5.0. Follow-up consisted of 3-montly CT- thorax scans and recurrence was evaluated using the RECIST-criteria. Cox-regression analysis and Kaplan-Meier analysis were used to calculate OS and PFS. Results 89 patients were included in the study. Mean age was 75.5 ± 7.6 years (range 55-90 years); 53% were men. The WHO PS was; 0 (7%), 1 (46%), 2 (36%) and 3 (11%). The mean tumor diameter was 2.9 ± 1.2 cm. Pathology was available in 62% of patients (28% squamous , 24% adenocarcinoma and 10% other). The mean lung dose was 7.4 ± 2.8 Gy , the mean heart dose 4.3 ± 5.4 Gy, and the maximum dose on the mediastinal envelope 64.6 ± 5.2 Gy. The 1-, 2-, 3-, 4- years overall survival (OS) and progression-free survival (PFS) were 79%, 60%, 50%, 40% and 71%, 65%, 58%, 51%, respectively. Local tumor recurrence after 1-, 2-, 3-, 4- year was 2.2%, 10.1%, 11.2%, 12.4%, respectively. Six patients (7%) had a toxicity grade 3 or more, classified as dyspnea (2) or radiation pneumonitis (4): 4 patients with grade 3 (5%), 1 with grade 4 (1%), and 1 with grade 5 (1%). No severe bleeding was observed. Conclusion This hypofractionated, accelerated fractionation schedule was as effective as SBRT with 3 year local control rates of 89%, but with less severe toxicity for centrally located early stage NSCLC. PO-1025 Prognostic factors for PFS and OS in radically treated patients with oligometastatic NSCLC M. LeenderS 1 , R. Robeers 1 , L. Hendriks 2 , J. Van Loon 1 , G. Bootsma 3 , R. Wanders 1 , C. Pitz 4 , B. Reymen 1 , R. Houben 5 , A. Van Baardwijk 1 , K. Verhoeven 1 , S. Peeters 1 , D. De Ruysscher 1 1 Maastro, Radiotherapy, Maastricht, The Netherlands ; 2 MUMC+, Pulmonology, Maastricht, The Netherlands ; 3 Zuyderland Medisch Centrum, Pulmonology, Heerlen, The Netherlands ; 4 Laurentius Ziekenhuis, Pulmonology, Roermond, The Netherlands ; 5 Maastro, Data Centre Management, Maastricht, The Netherlands Purpose or Objective Evidence suggest prolonged PFS and OS with oligometastatic non-small cell lung cancer (NSCLC) patients when treated with a radical approach with acceptable side effects. However only 15-25% may experience these beneficial effects. Identification of ‘true’ oligometastatic disease remains a gap in our knowledge. We therefore sought to determine prognostic factors and tried to create a first model. Material and Methods 170 stage IV NSCLC patients were included. All patients were staged with a whole body FDG-PET-CT scan and cerebral MRI. All patients received a radical treatment, surgery or radiotherapy. Systemic anti-cancer treatment was not mandatory. Oligometastatic stage was defined according to the EORTC definition; ≤5 metastatic lesions in ≤3 organs. Follow-up consisted of CT-thorax scans every 3-6 months and a consultation with the pulmonologist. Cox-regression analysis and Kaplan-Meier analysis were used to determine the prognostic factors. Results Mean age 66 ± 8.9 years and 58% was male. The median follow-up time for living patients was for OS 49 months and for PFS 51 months. 83% had a good WHO performance status (0-1) and 95% had only 1 metastatic site. The site of metastases were; brain (32%), lung (25%), bone (15%), adrenal gland (13) and lymph nodes (9%). Approximately half of the patients had an adenocarcinoma (53%), followed by squamous cell carcinoma (28%). The treatment sequence was 45% concurrent chemo-radiation therapy,