C77-16 Safety and Outcomes of Concurrent Chemoradiotherapy in Stage III Non-Small Cell Lung Cancer With Interstitial Lung Disease or Interstitial Lung Abnormalities: A Retrospective Analysis

Abstract Background Treatment-related lung injury is a major concern in patients with lung cancer complicated by interstitial lung disease (ILD) or interstitial lung abnormalities (ILA; subclinical interstitial changes identified on chest CT). In chemoradiotherapy (CRT) for stage III non-small cell lung cancer (NSCLC), severe radiation pneumonitis occurs in 20-40% of patients. We evaluated the incidence of treatment-related lung injury in ILD/ILA-complicated stage III NSCLC patients treated with CRT at our institution. Methods Among 79 patients deemed eligible for CRT between December 2018 and September 2025, 8 were excluded, mainly due to the presence of UIP pattern, leaving 71 patients for analysis. The observation period was defined from treatment initiation to confirmation of disease progression. Cases that did not meet the criteria for UIP pattern but demonstrated one of its characteristic CT findings—irregular interlobular septal thickening—were provisionally defined as having “UIP framework” and analyzed separately. Results The median age of 71 patients was 70 years (range 28-87), with 55 males. ILD/ILA was present in 26 patients, including 2 with UIP framework. Treatment-related lung injury occurred in 18 of 26 ILD/ILA patients (69%) and 26 of 45 non-ILD/ILA patients (57%). Among ILD/ILA patients, radiation pneumonitis occurred in 13 events (grade G1, 9; G2, 4), durvalumab-related lung injury in 4 events (G2, 3; G3, 1), and acute exacerbation of interstitial pneumonia in 1 event (G3). Both UIP framework patients developed lung injury, including acute exacerbation (G3) and durvalumab-related lung injury (G2). Non-ILD/ILA patients experienced mainly mild to moderate events: radiation pneumonitis in 23 events (G1, 20; G2, 3) and durvalumab-related lung injury in 6 events (G1, 1; G2, 3; G3, 1). There were no treatment-related deaths, regardless of the presence or absence of underlying ILD/ILA. Conclusions Among stage III NSCLC patients treated with CRT after exclusion of UIP cases, acute exacerbations of interstitial pneumonia occurred only in one patient with UIP framework. In contrast, treatment-related lung injury was mostly mild to moderate (grade 1-2) in patients without UIP framework, suggesting that CRT may be relatively safe in this population. Careful monitoring is warranted in patients with UIP framework because of their potential risk of acute exacerbation. This abstract is funded by: None