ESTRO 2025 - Abstract Book

S1364

Clinical - Lung

ESTRO 2025

2619

Digital Poster Impact of lung lobe proportion in total lung DVH parameters on radiation pneumonitis in definitive radiotherapy for lung cancer SACHIKO MIURA, Kazuya Inoue, Nobuhide Wakai, Youhei Kanamori, Nobuyoshi Inooka, Kaori Yamaki, Isao Asakawa, Tetsuro Tamamoto, Fumiaki Isohashi Radiation Oncology, Nara Medical University, Kashihara, Japan Purpose/Objective: The correlation between dose-volume histogram (DVH) parameters (V5 (volume receiving 5 Gy or more), V20, and mean lung dose (MLD)) for total lung and radiation pneumonitis (RP) is well established. However, the radiosensitivity differences among lung lobes remain poorly understood. Therefore, we investigate the association between lung lobe proportion in total lung DVH parameters and RP in definitive radiotherapy for unresectable non small cell lung cancer (NSCLC).

Material/Methods:

We retrospectively analyzed 146 patients with unresectable NSCLC who underwent definitive radiotherapy (excluding stereotactic body radiotherapy) at our institution between August 2018 and September 2023. Total lung values of V5, V20, and MLD were calculated. We then determined the lower lobe proportion (LLP) in total lung DVH parameters for V5 and V20. RP was graded according to CTCAE v5.0, and the correlation between RP of Grade 2 or higher and each parameter was analyzed. Results: RP of Grade 2 or higher was observed in 60 patients (41%). LLP was 25.7% (Interquartile Range (IQR): 16.2-37.1%) for V5 and 27.0% (IQR: 14.9-42.5%) for V20.