RAS-Like Radiological Findings in Lung Transplant Recipients with Preserved and Stable Lung Function

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<h3>Purpose</h3> Restrictive allograft syndrome (RAS) is the most severe phenotype of chronic lung allograft dysfunction (CLAD). RAS presents as permanent restrictive lung function decline with typical radiological findings such as apical fibrosis and traction bronchiectasis. We investigated the incidence and clinical impact of RAS-like radiological findings in lung transplant recipients with preserved and stable lung function. <h3>Methods</h3> 96 adult de novo lung transplant recipients transplanted between 2003-2015 who had not developed CLAD after a median time of 4.8 IQR 4.8 years from transplantation were retrospectively analysed. Serial computed tomography (CT) images were analysed for radiological RAS-like findings. In patients with RAS-like radiological findings, subsequent lung function was determined by spirometry, CLAD diagnosed if FEV1 decreased to <80% of best postoperative, and CLAD subtype and lung volume change was determined by CT volumetry. <h3>Results</h3> Of 96 lung transplant patients with preserved lung function, 6 (6.3%) had RAS-like signs. These CT findings first occurred at a median of 3.5 IQR 2.0 years after transplantation, initially consisted of apical fibrosis (100%) and later also traction bronchiectasis (50%) (Figure A). During follow-up of median of 5.0 IQR 4.0 years after the first RAS-like signs were seen in CT-images, no lung restriction was detected by CT-volumetry (Figure B), 3/6 patients developed CLAD that was subclassified as BOS, and all 6 patients were alive. <h3>Conclusion</h3> We detected radiological RAS-like findings in a subpopulation of lung transplant recipients that had preserved and stable lung function. Although some of these patients later develop CLAD, they did not progress to true RAS and had a favourable clinical course. These findings suggest that radiological RAS-like findings in stable lung transplant patients do not always result in rapid lung function decline, restrictive physiology and dismal clinical prognosis associated with true RAS.