ESTRO 2020 Abstract Book

S549 ESTRO 2020

after 1y that evolved there, after into mass-like pattern at the end of the follow-up.

limited pulmonary reserve often receive palliative treatment. To assess the feasibility of PET/CT-based image-guided moderate hypofractionated thoracic irradiation (Hypo-IGRT) in this cohort, we enrolled patients in a single-centre prospective study. Material and Methods Patients with stage IIB-IIIC node-positive NSCLC, Eastern Cooperative Oncology Group (ECOG) performance status (PS) of 2 or greater, FEV1 ≤ 1.0 L and/or DLCO-SB ≤ 40% and/or on long-term oxygen therapy (LTOT) were enrolled in the study. Highly conformal moderate hypofractionated image-guided thoracic irradiation (Hypo-IGRT) was delivered to intrathoracic macroscopic disease in 15 to 16 daily fractions to a total dose of 45 to 48 Gy (ICRU). Planning was based on 18F-FDG-PET/CT and 4D-CT in the treatment position. Vital capacity (VC), FEV1 and DLCO-SB were analyzed prior to, 3 and 6 months after Hypo-IGRT. Results Seventeen consecutive patients were enrolled and completed Hypo-IGRT. Median follow-up for the entire cohort was 6.4 months post-radiotherapy – although 4 patients had < 6 months FU. Median estimated PFS and 6- month PFS were 8.8 months and 10/13 (77%), respectively. Median OS and 6-month OS were not reached and 11/13 (85%), respectively. Treatment was well tolerated with 2/17 (12%) grade 2 and no grade ≥ 3 oesophagitis and 3/17 (18%) grade 2 and 1/17 (6%) grade ≥ 3 pneumonitis. Conclusion Hypo-IGRT consisting of 45 to 48 Gy in 15 to 16 daily fractions for node-positive NSCLC patients with poor PS and limited lung function was well tolerated. Comprehensive analysis of pulmonary function parameters is planned. Studies on long-term safety and efficacy of this treatment protocol are warranted. PO-1032 Clinical Features and Treatment Outcome of Resectable Pulmonary Large Cell Neuroendocrine Carcinoma J. Moon 1 , W.H. Lee 1 , B.M. Lee 1 , J. Lee 1 , A.J. Yang 1 , G. Yang 1 , J. Kim 1 , T.H. Kim 1 , N. Kim 1 , H.I. Yoon 1 , J.H. Cho 1 , C.G. Lee 1 , S.H. Choi 1 1 Yonsei Cancer Center, Radiation Oncology, Seoul, Korea Republic of Purpose or Objective Pulmonary large cell neuroendocrine carcinoma (LCNEC) was classified as a type of non-small cell lung cancer (NSCLC). However, recent studies have shown that its biological, clinical, and poor prognostic characteristics are more similar to those of small cell lung cancer (SCLC) and hence it was re-classified as a distinct neuroendocrine group. There is still a lack of consensus on the most appropriate treatment policy, due to the lack of literature data and their peculiar features. Here, we reviewed our institutional experiences and tried to suggest the appropriate treatment directions for resectable pulmonary LCNEC. Material and Methods A total of 72 patients who were pathologically diagnosed as pulmonary LCNEC between January 2005 and December 2018 were identified by reviewing medical records of all inpatients in the Yonsei cancer center. In this center, curative surgery was considered firstly for patients with early or some advanced-stage tumors with resectable status, unless they were medically inoperable. 39 patients with stage I-III LCNEC underwent curative resection of the primary tumor, and these patients were included in this study cohort. Adjuvant treatment option was decided as the physician’s preference, considering each patient’s clinical and pathologic features. Results Of 39 patients whose median age was 67, 18 (46%), 12 (31%), and 9 (23%) patients were stage I, II and III respectively. In stage I, 6 (33%) patients received surgery alone, and 12 (67%) patients received adjuvant CTx. With

The incidence of high risk characteristics on CT images during the follow-up is not negligible (Tab1) as details Tab1 with the n, wherever just 3/56 pts were diagnosed as local failure and 3/56 pts with distance progression. Tab1, HRF incidence Characteristic 6- 11m 12- 23m 24- 35m >36m None HRF 25 16 7 4 Enlarging opacity 10 6 7 2 Sequential enlargement 0 2 0 1 Enlargement after 12m 0 3 4 2 Bulging margin 3 2 2 1 Linear Margin disappearance 3 2 1 0 Loss air bronchogram 18 15 11 3 Cranio-Caudal growth 2 1 2 0 Conclusion Any degree of chronic change is nearly universal in the literature and we confirm this in our patients, and it often continues to evolve more than 1 year post-SBRT. Clinicians should be aware of these radiological findings and be familiar with the presence of High risk characteristics on the CT, which need to be distinguished from the cases of local failure post-SBRT. PO-1031 Initial report on feasibility of Hypo-IGRT in stage IIB-III NSCLC pts with poor PS & lung function C. Eze 1 , J. Taugner 1 , N. Schmidt-Hegemann 1 , O. Roengvoraphoj 1 , L. Käsmann 1 , M. Dantes 1 , M. Li 1 , C. Belka 1 , F. Manapov 1 1 University hospital- LMU Munich, Department of Radiation Oncology, Munich, Germany Purpose or Objective Patients with node-positive NSCLC who are unsuitable candidates for definitive chemoradiotherapy (CRT) or surgical resection due to poor performance status and