A39-11 Imaging Characteristics of Trastuzumab Deruxtecan (T-DXd)-Induced Interstitial Lung Disease in Breast Cancer: A Real-World Clinical Study

Abstract Rationale Trastuzumab deruxtecan (T-DXd) is an antibody-drug conjugate targeting HER2 and is widely used for cancers including breast, lung, colorectal, and gastric cancer. However, T-DXd administration is associated with a risk of drug-induced interstitial lung disease, complicating clinical management. A comprehensive description of the high-resolution computed tomography (HRCT) features of T-DXd-induced interstitial lung disease (T-IILD) remains limited. This study aims to evaluate the HRCT characteristics of T-IILD in patients with breast cancer, focusing on the presence of pre-treatment interstitial lung abnormalities (ILA) and their association with the development of T-IILD. Methods We retrospectively reviewed the clinical data for patients with breast cancer who received T-DXd at our hospital between May 2020 and May 2025 and underwent HRCT before and after T-DXd treatment. Baseline HRCT was assessed for pulmonary abnormalities, including ILA, and post-treatment HRCT was evaluated for changes indicative of T-IILD. Patients with confirmed T-IILD were compared with those without. Results A total of 158 female patients with breast cancer received T-DXd, with a median age of 56 years (range: 27-77 years). Baseline HRCT showed no evidence of interstitial lung disease in any patient; however, subtle pulmonary abnormalities suggestive of ILA were identified in 52 patients (32.9%). During treatment, T-IILD developed in 32 patients (20.3%). Among these patients, the median age was 60 years (range: 45-72 years). Twenty-four of 52 patients with baseline ILA (46.2%) and 8 of 106 without ILA (7.5%) developed T-IILD. The incidence of T-IILD was significantly higher in patients with ILA (odds ratio, 10.30; 95% CI, 3.96-29.62; p 0.001). The characteristic HRCT findings of T-IILD were bilateral, diffuse, and non-segmental ground-glass opacities that were faint in appearance. No deaths attributable to T-IILD occurred during follow-up. Conclusion The presence of ILA on baseline HRCT may serve as a marker for identifying patients at higher risk for T-IILD. Screening for ILA before treatment may facilitate safer administration of T-DXd and enable earlier recognition and management of T-IILD. This abstract is funded by: None