ESTRO 2022 - Abstract Book

S1073

Abstract book

ESTRO 2022

R. Wooder 1 , N. Bayman 2 , C. Chan 2 , J. Coote 2 , C. Faivre-Finn 2 , M. Harris 2 , S. O'Hare 3 , L. Pemberton 2 , A. Salem 2 , H. Sheikh 2 , M. Sumner 3 , S. Tenant 4 , D. Woolf 2 1 The Christie NHS Foundation Trust, Christie medical physics and engineering , Manchester, United Kingdom; 2 The Christie NHS Foundation Trust, Networked services, clinical oncology, Manchester, United Kingdom; 3 The Christie NHS Foundation Trust, Christie medical physics and engineering, Manchester, United Kingdom; 4 The Christie NHS Foundation Trust, Radiology, Manchester, United Kingdom Purpose or Objective As the capabilities of diagnostic imaging have advanced, higher levels of spatial resolution identify smaller lung abnormalities. Radiation oncologists are treating smaller and more ill defined targets. Many patients with lung cancer will have a background of chronic lung disease with associated abnormalities (e.g. small equivocal nodules) identified at the time of the RT planning scan. Guidance in the UK recommend references to image slices in the radiology reports to help the reader clearly identify abnormalities but this is not compulsory. Materials and Methods A retrospective review of the CT and PET reports of thirty patients ( 4 metastatic and 26 primary lung cancer) who received lung SABR to ascertain if the target lesion was clearly identified with a slice reference number. Results 24 patients (80%) had a slice reference number clearly identifying the target lesion. Out of theses 8 had detailed reports with slice reference numbers identifying the target lesion and benign abnormalities or areas requiring surveillance. 7 patients out of 30 had additional lesions visible on the RT planning scan which had previously been reported on diagnostic imaging and under surveillance. There was no slice reference number clearly distinguishing the lesion requiring treatment and that under surveillance for 3 of these patients. Conclusion Slice reference numbers were included in most but not all radiology reports. Where there are multiple lesions under surveillance slice reference numbers are beneficial in target lesion identification. Inclusion of slice reference numbers could be advocated as part of an error reduction strategy which would reduce the risk of the target being incorrectly delineated. 1 SNU-SMG Boramae medical center, radiation oncology, seoul, Korea Republic of; 2 Seoul National University College of Medicine, Radiation Oncology, Seoul, Korea Republic of; 3 SNU-SMG Boramae medical center, Radiation Oncology, Seoul, Korea Republic of Purpose or Objective In the treatment of concurrent chemoradiotherapy (CCRT) in limited-stage small cell lung cancer, the optimal once-daily radiotherapy (RT) dose/fractionation remain unclear although it is the most frequently used. Therefore, this study aimed to compare the treatment outcomes and toxicities of modest dose RT ( ≤ 54 Gy) with those of standard dose RT (>54 Gy) and investigate the benefit of the high dose based on patient factors. Materials and Methods Since 2004, our institution has gradually increased the thoracic RT dose. Among the 225 patients who underwent CCRT, 84 patients (37.3%) received >54 Gy. Because the patients treated with RT > 54 Gy were not randomly assigned, propensity score matching (PSM) was performed. Results The proportion of patients treated with >54 Gy increased over time (p = 0.014). Multivariate analysis revealed that the overall tumor stage and dose > 54 Gy (hazard ratio 0.65, p = 0.029) were independent prognostic factors for overall survival (OS). PSM confirmed that thoracic RT doses of >54 Gy showed significantly improved progression-free survival (3-year rate, 40.0% vs 22.7%, p = 0.004) and OS (3-year rate, 52.4% vs 38.5%, p = 0.029). However, in patients with underlying lung disease, OS benefit from >54 Gy was not observed but considerable rates of severe pulmonary toxicities were observed (p = 0.001). Conclusion Delivery of a standard once-daily dose of 60 Gy should be considered in general. However, a modest dose of ~54 Gy may be sufficient for frail patients with underlying lung disease. Further study is needed to validate these results. PO-1274 Is a once-daily RT dose optimal for patients with underlying lung disease in limited-stage SCLC? B.H. Kim 1 , J. Chung 2 , S. Kim 3 , H. Wu 2 , H.J. Kim 2

PO-1275 Acute toxicity associated to hypofractionation vs. standard fractionation in lung cancer treatment

M.M. Teja Ubach 1 , M. González Cantero 1 , M.I. Garrido Botella 1 , M. Rodríguez Roldán 1 , Á. Manso de Lema 1 , R. Matute Martín 1 , I. Rodríguez Rodríguez 1 , E. González del Portillo 1 , R. Morera López 1