The role of 18F-FDG PET-CT in predicting progressive pulmonary fibrosis in idiopathic inflammatory myopathy associated interstitial lung disease

Aim This study aims to investigate the role of 18 F-FDG PET-CT in the development of progressive pulmonary fibrosis (PPF) in patients with idiopathic inflammatory myopathy-associated interstitial lung disease (IIM-ILD) and to develop a predictive nomogram model. Methods This study retrospectively included patients diagnosed with IIM-ILD who underwent 18 F-FDG PET-CT at Ruijin Hospital between 2018 and 2024. The baseline characteristics, IIM types, myositis antibodies, laboratory tests, pulmonary function, ILD subtypes, 18 F-FDG PET-CT findings, and treatment were collected. Enrolled patients were divided into PPF and non-PPF groups according to diagnostic criteria. Clinical features were compared between the two groups, and logistic regression analysis was performed to identify risk factors for PPF. All identified risk factors were combined to construct the predictive nomogram. Receiver operating characteristic curve, calibration plot, and decision curve analysis were used to evaluate the accuracy and efficiency of this predictive model. Additionally, we drew the survival curve of PPF and non-PPF, and compared the maximum standardized uptake value (SUV max ) between short-term death and long-term survival. Results A total of 71 eligible IIM-ILD patients were included, of whom 29 developed PPF within one year of follow-up. Multivariate analysis revealed that bilateral lung SUV max and FVC%pred were associated with the occurrence of PPF. The calibration plot demonstrated excellent agreement between the predicted and actual observed probability of PPF (Hosmer–Lemeshow test: P = 0.143). The predictive nomogram achieved an area under the curve of 0.887 (95% CI : 0.805–0.969). The SUV max in the lungs was significantly higher in the PPF group than in the non-PPF group ( P < 0.001). Moreover, lung SUVmax was significantly higher in patients who died within one year than in those who survived for more than five years ( P = 0.014). In addition, patients with PPF had a significantly lower survival rate than those without PPF ( P = 0.040). Conclusion 18 F-FDG PET-CT and FVC% pred are associated with the occurrence of PPF. The prognosis of PPF is poor, and high SUV max is correlated with short-term mortality. Exhibiting robust discrimination and calibration, this nomogram holds potential for clinical application.