Complicated Silicosis due to silica agglomerates: 18F-FDG PET/CT and systemic inflammatory indices.

The role of Positron Emission Tomography/Computed Tomography using F18-fluorodeoxyglucose (FDG-PET/CT) in silicosis has been barely studied. Also, the relation of metabolic activity measured by maximum standardized uptake value (SUVmax) and systemic inflammatory indices is unknown. We aimed to investigate this topic. <bold>Methods:</bold> 17 patients with complicated silicosis were enrolled. All had worked for at least 5 years finishing and installing silica agglomerate benchtops. At the time of the study, exposure had ceased for at least 7 years. Clinical data, PET/CT, respiratory function test and blood samples were taken. <bold>Results:</bold> Patient mean age: 44±5.4 and all were male. Years of exposure:10.94±3.2. Progressive Massive Fibrosis category (ICOERD): A 5 patients, B 6 and C 6. The average SUVmax of the main pulmonary lesions was 6.32±3.04. All patients had mediastinal lymphadenopathies with high metabolic activity, 12 supraclavicular, 8 lower thoracic and 12 abdominal. The average SUVmax of lymphadenopathies was 6.22±1.56. Spearman's correlation analysis between the average SUVmax of lung and LMR (Lymphocyte-to-Monocyte Ratio) was -0.506(p=0.038) and SIRI (Systemic Inflammatory Response Index) was 0.559(p=0.02). The correlation between the average SUVmax of lymphadenopathies and LMR was -0.482(p=0.05) and AISI (Aggregate Index of Systemic Inflammation) was 0.498(p=0.042). <bold>Conclusions:</bold> Metabolic activity of lung lesions and lymphadenopathies is high even years after exposure cessation. Lymphadenopathies are not limited to the thoracic cavity. The correlation between metabolic activity and systemic inflammatory indices opens a new avenue of research. Grant:ISCIII PI19/01064