FDG-PET/CT in the prediction of pulmonary function improvement in nonspecific interstitial pneumonia. A Pilot Study

Our study aimed to analyse the characteristics of nonspecific interstitial pneumonia (NSIP) using FDG-PET/CT (PET) and to evaluate its ability to predict the therapeutic response.

Eighteen NSIP patients were included. Maximum standardized uptake value (SUV_max), FDG uptake extent (in percentage of lung volume), high resolution CT scan (HRCT) elementary lesions, and HRCT fibrosis score were recorded. The predictive value of the parameters for lung function improvement was evaluated using logistic regression and Receiver Operating Characteristic (ROC) curve analysis (n=13/18).

All patients had an increased pulmonary FDG uptake (median SUV_max=3.1 [2-7.6]), with a median extent of 19% [6-67]. Consolidations, ground-glass opacities, honeycombing and reticulations showed uptake in 90%, 89%, 85% and 76%, respectively. FDG uptake extent was associated with improvement of pulmonary function under treatment (increase in forced vital capacity>10%, p=0.03), whereas SUV_max and HRCT fibrosis score were not (p>0.5). For FDG uptake extent, ROC analysis showed an area under the curve at 0.85±0.11 and sensitivity/specificity was 88%/80% for a threshold fixed at 21%.

Increased FDG uptake was observed in all NSIP patients, both in inflammatory and fibrotic HRCT lesions. The quantification of FDG uptake extent might be useful to predict functional improvement under treatment.