CT ASSESSMENT OF BODY COMPOSITION AND LUNG EVOLUTION IN CYSTIC FIBROSIS AFTER ELEXACAFTOR-TEZACAFTOR-IVACAFTOR: A COHORT STUDY.

BACKGROUND: Elexacaftor-Tezacaftor-Ivacaftor (ETI) therapy markedly improves pulmonary function in people with cystic fibrosis (pwCF) but induces weight gain, raising concerns about body composition. CT scans routinely performed to assess lung structure offer opportunistic nutritional assessment. In this study, we aimed to evaluate changes in body composition in pwCF after ETI through CT image analysis, and changes in radiological findings measured by the Bhalla score. METHODS: This observational study analyzed paired chest CT scans at the T12 vertebra level from 32 adult pwCF before and after ETI initiation. Body composition was quantified using FocusedON artificial intelligence-assisted software, assessing muscle, subcutaneous (SAT), visceral (VAT), and intermuscular adipose tissue (IMAT) areas, percentages, and Hounsfield units (HU). Muscle quality was stratified by attenuation. Respiratory status was evaluated via Bhalla score, spirometry, and bacterial colonization status. RESULTS: Post-ETI, weight (+4.1 kg) and BMI (+1.5 kg/m2) increased significantly (p<0.001), mainly reflecting increases in IMAT (from 0.3% to 0.5%), SAT (from 7.5% to 9.3%) and VAT (from 6.9% to 9.4%) percentages (p<0.05). Muscle area and lean muscle area also increased significantly, although their relative percentages did not change significantly. Normal attenuation muscle significantly decreased (69.9 vs. 64.7%, p=0.043), suggesting myosteatosis. Respiratory changes included improvements in FEV1 (+11.8%), FVC (+12.5%), Bhalla score (+3.7 points) (p<0.001), and reduced colonization (78.1 vs. 43.8%, p=0.004). CONCLUSIONS: ETI promotes adiposity-dominant weight gain with radiological features suggestive of myosteatosis, alongside robust lung improvements. FocusedON CT image analysis promotes integrated nutritional-radiological insights, supporting personalized CF care, although further validation is needed.