Lung ¹⁸ F-FDG uptake correlates with lung function alteration in patients with IPF

Purpose: Idiopathic pulmonary fibrosis (IPF) is a progressive disease with a very poor prognosis. Non-invasive markers of prognosis are lacking. We assessed lung 18 F-FDG uptake in patients with IPF. Methods: The maximal (SUVmax) and the mean (SUVmean) lung 18 F- FDG uptake was measured in each lung, as a standardized uptake value, in 28 consecutive patients with IPF, diagnosed according to the 2011 ATS/ERS/JRS/ALAT guidelines, and compared with normal lung from 15 control patients with extra-thoracic neoplasm. Lung function tests, bronchoalveolar lavage and HRCT results were obtained within one month. HRCT fibrosis and ground glass were scored according to Kazerooni et al (Kazerooni et al, American Journal of Roentgenology .1997 :169 ; 977-933) Results: An increased lung uptake of 18 F-FDG was measured in IPF patients either for SUV mean (1.01±0.06 vs 0.50±0.02, p<0.00001, unpaired t-test) or SUV max (2.83±0,12 vs 1.83±0.11,p<0.0001). FVC (%) and DLCO (%) negatively correlated with SUV mean (respectively r=-0.48 [-0,73;-0,12] p=0,01; r=-0.63 [-0,82;-0,31], p=0,0008, Pearson test) and SUV max (respectively, r=-0,51, [-0,75;-0,15] p=0,008; r= -0,59 [-0,79;-0,25] p=0,002). Left lower lobe fibrosis score correlated with SUV mean (r= 0,58, [0,23;0,80],p=0,002) but right lower lobe did not (r=0,21, [-0,17;0,54],p=0,27) . Pulmonary 18 F- FDG uptake did not correlate with BAL cytology, lung function decline or survival. Conclusion Our results indicate that lung 18 F-FDG uptake correlates with lung function alteration and lung fibrosis score but does not predict outcome in patients with IPF.