BackgroundInterstitial lung diseases (ILD) it’s a frequent complication in connective tissue diseases (CTD) such as rheumatoid arthritis (RA) or systemic sclerosis (SS), but the lung is the only affected organ in the idiopathic pulmonary fibrosis (IPF). Nonspecific interstitial pneumonia (NSIP) is the more frequent form in SS while usual interstitial pneumonia (UIP) predominates in RA patients and in the IPF form. Some studies suggested that 18-FDG-PET/CT could help to detect zones of activity in lung tissue in IPF and this in turn could predict the disease progress, but results are inconclusive. Moreover, little is known about the value of 18-FDG PET uptake in ILD associated to RA or SS.ObjectivesThe purpose of this study is to evaluate the predictive value of 18 FDG-PET/CT scan images in functional pulmonary progression of ILD associated to RA or SS.MethodsWe conducted a 12 month prospective observational study on patients diagnosed with ILD associated to SS or RA between January 2015 and May 2017. ILD diagnosis was based on clinical assessment, pulmonary function tests (PFTs) and expert HRCT evaluation. We performed three visits: basal, 6 month and 12 month. On all visits a general exploration, forced vital capacity (FVC) and diffusing capacity of the lungs for carbon monoxide (DLCO) were carried out. On basal and 6 month visit a 18-FDG-PET/TC was performed within a period of three months from the PFTs. Patients continued with their treatment (corticosteroids, DMARDs or immunosuppressants). The nuclear medicine physician identified the maximum and mean standardised uptake value (SUVmax and SUVmean) in the three areas with the most FDG uptake, and adenopathies uptake. PET/CT images were reviewed by 2 combined radiologist/nuclear medicine physicians in consensus.ResultsWe included 17 patients, 10 had UIP associated with RA and 7 NSIP related to SS. It appeared that RA patients had longer lung illness evolution and worse FVC than SS patients (table 1), in spite of not having found statistical differences. We detected significant statistical relation between the highest SUVmax and FVC (p=0.009) or DLCO progression (p=0.006) in SS patients, independently of the basal FVC and DLCO, and duration of lung illness in a multivariable linear mixed model. We didn’t find any relation between SUVmax and FVC or DLCO progression in RA patients.ConclusionsIn our cohort of patients with SS, 18 FDG PET/TAC can aid in predicting the progression of ILD associated disease, which does not occur in RA patients.Disclosure of InterestNone declared