18F-FDG PET/CT in Pulmonary Sarcoidosis:Quantifying Inflammation by the TLG index

ABSTRACT

Objectives: In sarcoidosis progressive pulmonary disease affects prognosis. Pulmonary disease activity estimated by classic means poorly predicts severity and progressiveness. ¹⁸F-fluoro-2-deoxyglucose-positron-emission-tomography computed-tomography (¹⁸F-FDG-PET/CT) estimates pulmonary activity by inflammatory-cells metabolism. We aimed to investigate pulmonary sarcoidosis by ¹⁸F-FDG-PET/CT and evaluate the role of total-lesion-glycolysis (TLG) value, as an index quantifying the whole burden of lung inflammation.

Methods: This is a retrospective study of sequentially gathered data. From a Greek cohort of 195 sarcoidosis-patients, 87 were identified with lung increased ¹⁸F-FDG uptake and further studied.

Results: Visualizing lung by ¹⁸F-FDG-PET/CT identified new imaging patterns and revealed activity in all Scadding stages. Ever-smokers presented significantly higher TLG and lower DLCO compared to never-smokers. However, TLG value did not correlate with functional indices and did not differ between symptomatic and non-symptomatic patients. Among treatment-naïve patients, TLG did not differ significantly in those requiring therapy compared to those remained off.

Conclusion: ¹⁸F-FDG PET/CT improved imaging and detection of pulmonary involvement and through TLG value revealed the deleterious smoking effect. The fact that TLG neither detected patients with clinical symptoms and functional impairment nor identified those requiring treatment once again confirms that in pulmonary sarcoidosis the link between activity, severity and decision to treat still eludes us.

KEYWORDS:

• ¹⁸F-FDG-PET/CT
• total lesion glycolysis value
• sarcoidosis pulmonary activity
• smoking
• SUV

Article highlights

• In sarcoidosis progressive pulmonary disease affects prognosis. Pulmonary disease activity estimated by classic means poorly predicts severity and progressiveness.

• ¹⁸F-fluoro-2-deoxyglucose positron-emission-tomography computed-tomography (¹⁸F-FDG-PET/CT) estimates pulmonary activity by inflammatory-cells metabolism.

• Visualizing lung by ¹⁸F-FDG-PET/CT identified new imaging patterns and revealed activity in all Scadding stages.

• ¹⁸F-FDG PET/CT improved imaging and detection of pulmonary involvement and through the TLG value revealed the deleterious effect of smoking in the lung.

• The fact that the TLG neither detected patients with clinical symptoms and functional impairment nor identified those requiring treatment once again confirms that in pulmonary sarcoidosis the link between activity, severity and decision to treat still eludes us.

Author’s contributions

SAP conceived of the study, had substantial contribution at the analysis and interpretation of data and wrote the final version of the manuscript, EDM had substantial contribution to the acquisition, the analysis and interpretation of data, supervised the accuracy and integrity of any part of the work, coordinated the study team and drafted parts of the final version of the manuscript, NP contributed to the performance of ¹⁸F-FDG PET/CT of all patients, contributed to the acquisition and interpretation of data for the work and drafted parts of the manuscript, MK developed a computer aided detection algorithm in-house for the detection of lung sarcoidosis in PET/CT images and the calculation of the MLV, SUV_mean, and TLG, contributed substantially to the acquisition of data, drafted part of the manuscript and revised critically this work for important intellectual content AIP performed the statistical analysis of the data, contributed substantially to the interpretation of data for the work and drafted parts of the manuscript, AG performed ¹⁸F-FDG PET/CT of all patients and contributed to the acquisition, analysis, and interpretation of data for the work and drafted parts of the manuscript, KM, NLK, and EG contributed substantially to the acquisition of data and revised critically this work for important intellectual content, SC was responsible for the performance of ¹⁸F-FDG PET/CT of all patients, had substantial contribution at the analysis and interpretation of data, drafted parts of the manuscript and revised critically this work for important intellectual content. All authors read and approved of the final version of the submitted publication.

Declaration of interest

The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.

Reviewer disclosures

Peer reviewers on this manuscript have no relevant financial or other relationships to disclose.

Additional information

Funding

This paper was not funded