Abstract / Summary
Idiopathic pulmonary fibrosis (IPF) is characterised by a variable and unpredictable clinical course. While GAP (gender, age, physiology) score remains the clinical standard for staging, it does not provide real-time insight into lesion metabolic activity. This study evaluates the correlation of 18 F-fluorodeoxyglucose uptake in positron emission tomography/computed tomography ( 18 F-FDG PET/CT) with GAP score, while also investigating whether maximum standardised uptake values (SUVmax) within fibrotic lesions can predict clinical severity and patient outcomes. We retrospectively analysed 30 patients diagnosed with IPF who underwent 18 F-FDG PET/CT for suspected comorbid disease. Metabolic activity was quantified via raw SUVmax in fibrotic lung parenchyma, while clinical severity was staged using GAP scoring. Correlation was assessed using Spearman’s rank coefficient (ρ). PFS and OS outcomes were analysed in the whole cohort ( n = 30) and an antifibrotic-treated subgroup ( n = 19) using the Mantel-Cox log-rank test where a median-split SUVmax 2.53 and 2.75 respectively defined “high” and “low” metabolic activity. Significant positive correlation was observed between GAP score at PET/CT index and fibrotic SUVmax (Spearman’s ρ = 0.448, p = 0.013), indicating that intensity of metabolic activity reflects clinical disease severity. While not statistically significant, exploratory survival findings suggest high SUVmax in fibrotic lesions could be correlated with shorter PFS than low SUVmax (25 vs. 50 months) with increased hazard of progression (HR: 3.68; 95% CI: 0.74–18.43; log-rank p = 0.089) in the antifibrotic-treated subgroup. Our results suggest that the assessment of lung tissue metabolic activity in 18 F-FDG PET/CT provides a potential imaging metric for disease severity. Our findings demonstrate an exploratory association between fibrotic-lung 18 F-FDG uptake and baseline GAP clinical severity. Larger prospective studies are required to determine whether molecular imaging can provide additive prognostic value in IPF.