The role of FDG PET-CT in differential diagnosis of pleural pathologies

Our plain-English summary of The role of FDG PET-CT in differential diagnosis of pleural pathologies, by U. Elboga, M. Yılmaz, M. Uyar, et al (Revista Española de Medicina Nuclear e Imagen Molecular, 2012).

The study

• Authors: U. Elboga, M. Yılmaz, M. Uyar, Y. Zeki Çelen, K. Bakır, O. Dikensoy
• Journal: Revista Española de Medicina Nuclear e Imagen Molecular
• Published: 2012;31(4):187-91
• Cited by: 13 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Objective: This study has aimed to evaluate the impact of (F18) Fluorodeoxyglucose Positron Emission Tomography-Computed Tomography (FDG PET-CT) in the differential diagnosis of malignant and benign pleural lesions in patients with suspected malignant pleural mesothelioma (MPM).

Material And Methods: Fifty patients (32 females, 18 males; age range 24-79 years) with pleural thickening, fluid, plaques or calcification on previous CT scan were examined with FDG PET-CT. PET-CT imaging was obtained 1 h after FDG injection. In 12 patients, delayed imaging from the thoracic region was performed 2 h after injection. FDG uptake was evaluated visually and semiquantitively using standardized uptake value (SUV). FDG PET-CT findings were compared with histopathologic diagnosis.

Results: Thirty-nine patients had increased FDG uptake in pleural lesions but PET-CT results were negative in 11 patients. When compared with histopathological results in FDG positive group, 34 patients had MPM, 5 had benign pathology; in FDG negative group 8 patients had benign pathology, 3 had MPM. Of patients with delayed imaging, 9 showed increased SUV but 3 had a decreased SUV on delayed images. Increased SUV group had 4 MPM, 5 benign pathology (3 chronic granulomatous inflammation, 2 benign asbestotic plaque). Decreased SUV group all had benign pathology (fibrosis, chronic inflammation, myofibrosis).

Discussion: FDG PET-CT is a useful imaging modality in differential diagnosis of malignant and benign pleural lesions. Delayed imaging seems to be useful if there is a decrease in SUV suggesting a benign pathology but does not seem to contribute to the differential diagnosis if the SUV is increased.

Copyright © 2011 Elsevier España, S.L. and SEMNIM. All rights reserved.

In plain English

This was a retrospective study from Gaziantep University in Turkey. The authors reviewed 50 patients (32 women, 18 men, aged 24 to 79) with pleural masses, thickening or fluid who had FDG PET-CT scans between January 2007 and March 2009 for suspected malignancy. They compared the scans with biopsy results. A lesion counted as positive when its standardized uptake value (SUV) was 2.5 or higher. Of 39 positive patients, 34 had malignant pleural mesothelioma and 5 had benign disease. Of 11 negative patients, 8 had benign disease and 3 had mesothelioma. Sensitivity was 91.8% and specificity 61.5%. The text attributes the false positives to tuberculosis pleuritis (3) and what it calls benign asbestosis plaque (2), but its table lists different diagnoses. Twelve patients whose uptake was borderline were scanned again after 2 hours. The 3 whose uptake fell all had benign disease. Patients' asbestos exposure was not reported. The authors concluded that FDG PET-CT is useful for telling malignant from benign pleural lesions, and that delayed imaging seemed useful when uptake decreased but not when it increased.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Retrospective diagnostic study comparing FDG PET-CT results with histopathology (biopsy) results
• Who was studied: 50 patients (32 female, 18 male; age 24 to 79, mean 57.6) with pleural mass, pleural thickening or pleural effusion, referred to the Nuclear Medicine Department of Gaziantep University, Turkey, between January 2007 and March 2009
• Exposure: The study evaluated an imaging test, FDG PET-CT (296 to 555 MBq of FDG injected intravenously), not asbestos exposure. No fiber type or individual asbestos exposure was reported for the patients. The introduction notes asbestos-containing soils in settlements around Gaziantep.
• Main results:
  • A lesion was called FDG positive if its SUV was 2.5 or higher. Of the 39 FDG-positive patients, 34 had malignant pleural mesothelioma and 5 had benign pathology.
  • Of the 11 FDG-negative patients (SUV below 2.5), 8 had benign pathology and 3 had malignant pleural mesothelioma. In those 3 patients, mesothelioma with low FDG uptake gave false negative results.
  • For malignant pleural mesothelioma, FDG PET-CT had sensitivity 91.8%, specificity 61.5%, accuracy 84%, positive predictive value 87.1% and negative predictive value 72.7% (34 true positive, 8 true negative, 5 false positive, 3 false negative, out of 50).
  • Delayed imaging at 2 hours was done in patients with borderline increased FDG uptake in pleural masses (12 patients).
  • Of the 12 patients with delayed imaging, 9 showed increased SUV. Of these, 4 had mesothelioma and 5 had benign pathology (given in the abstract as 3 chronic granulomatous inflammation and 2 benign asbestotic plaque).
  • All 3 patients whose SUV decreased on delayed imaging had benign pathology.
  • Distant metastases were detected with PET-CT in 4 mesothelioma patients (10.8%).
• The authors' conclusion: The authors concluded that FDG PET-CT is a useful imaging method for distinguishing malignant from benign pleural lesions. They found delayed imaging seemed useful when SUV decreased, suggesting benign disease, but did not seem to help when SUV increased.
• Limitations the authors state:
  • Active granulomatous inflammation can mimic tumors by showing high metabolic activity, causing false positive results.
  • Small tumors can be missed because PET has limited spatial resolution.
  • A decreased SUV on delayed imaging may support a benign diagnosis, but its contribution to clinical management is limited.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Pleural plaques and thickening.

Medical terms in this study, explained in our Lexicon: PET-CT, Differential Diagnosis, Pleural Mesothelioma, Pleural Thickening, CT Scan, Pathology, Inflammation, Fibrosis.

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