Assessment of intrathoracic lymph nodes by FDG PET/CT in patients with asbestos-related lung cancer

Our plain-English summary of Assessment of intrathoracic lymph nodes by FDG PET/CT in patients with asbestos-related lung cancer, by N. Iga, H. Sonobe, D. Mizuno, et al (Journal of Thoracic Disease, 2021).

The study

• Authors: N. Iga, H. Sonobe, D. Mizuno, H. Nishi
• Journal: Journal of Thoracic Disease
• Published: 2021;13(10):5925-5932
• Cited by: 3 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Background: This study explored the assessment of intrathoracic lymph node metastasis by 18F-fluoro-2-deoxy-D-glucose (FDG) positron emission tomography computed tomography (PET/CT) in patients with asbestos-related lung cancer (ARLC).

Methods: We retrospectively reviewed the data on 35 patients with ARLC who underwent preoperative FDG-PET/CT and surgical resection between January 2012 and December 2018. We collected medical information from medical records and imaging systems and examined the FDG uptake in each lymph nodal region resected by surgery and the presence or absence of pathological lymph node metastasis.

Results: Pathological lymph node metastases were detected in 14 (8.70%) of 161 nodal stations. The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of FDG-PET/CT were 71.4% (10/14), 87.8% (129/147), 35.7% (10/28), 97.0% (129/133), and 86.3% (139/161), respectively. Six of the eight false-positive patients had bilateral accumulations, whereas all six true-positive patients had unilateral accumulation (P=0.006). On histopathological examination, the false-positive nodes showed disruption of lymphoid follicles in the cortex, infiltration of histiocyte-like cells in the medulla, fibrous micronodules, and severe anthracosis.

Conclusions: PET/CT scans of patients with ARLC showed comparable sensitivity and specificity to those of PET/CT scans of patients with conventional lung cancer reported in the literature. Many false-positive cases also showed bilateral symmetric accumulation. This method can be used to evaluate lymph node involvement in lung cancer.

2021 Journal of Thoracic Disease. All rights reserved.

In plain English

This retrospective study from Japan examined how well FDG PET/CT scans identified cancer spread to chest lymph nodes before surgery in 35 men with asbestos-related lung cancer operated on between January 2012 and December 2018. All had been exposed to asbestos but not to coal or silica. Scan results were compared with microscope findings in 161 lymph node stations removed at surgery. Cancer was found in 14 of the 161 stations. The scan's sensitivity was 71.4% (10/14), specificity 87.8% (129/147), positive predictive value 35.7% (10/28), negative predictive value 97.0% (129/133) and accuracy 86.3% (139/161). Eighteen stations, in eight patients, were false positives. Six of those eight patients had uptake on both sides of the chest, while all six patients with correctly detected spread had uptake on one side (P=0.006). All patients with false-positive nodes had severe anthracosis (dark pigment deposits) in them. The authors concluded that sensitivity and specificity were comparable to those reported for conventional lung cancer. They noted that this cancer is rare and more case series are needed.

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 observational study comparing preoperative FDG PET/CT findings with pathology of surgically removed lymph node stations
• Who was studied: 35 men with asbestos-related lung cancer (ARLC, as defined by Japanese criteria) who had surgery at Okayama Rosai Hospital, Japan, between January 2012 and December 2018. The text gives their age as a 'mean' of 73 years (interquartile range 70 to 78), while Table 1 calls it a median. All had asbestos exposure but no coal or silica exposure.
• Exposure: Occupational asbestos exposure, measured as asbestos bodies per gram of dry lung tissue: median 13,061 (interquartile range 6,039 to 61,097). Fiber types were not reported. The most common jobs were dockyard work (13), construction (5) and pipework (5).
• Main results:
  • Cancer spread (metastasis) was found by pathology in 14 of 161 removed lymph node stations (8.70%).
  • Per lymph node station, FDG PET/CT had sensitivity 71.4% (10/14), specificity 87.8% (129/147), positive predictive value 35.7% (10/28), negative predictive value 97.0% (129/133) and accuracy 86.3% (139/161).
  • There were 4 false-negative and 18 false-positive lymph node stations.
  • Six of the 8 patients with false-positive nodes had uptake on both sides of the chest. All 6 patients with true-positive nodes had uptake on one side only (P=0.006).
  • Lymph node short diameter on chest CT was significantly larger in true-positive nodes than in false-positive nodes (P=0.008). Size of the dissected nodes did not differ significantly.
  • Asbestos body counts did not differ significantly between patients with false-positive nodes (median 12,508 per gram dry lung) and those with true-positive nodes (median 16,452 per gram), P=0.747.
  • False-positive nodes showed disruption of lymphoid follicles in the cortex, histiocyte-like cells in the medulla, fibrous micronodules and severe anthracosis. All patients with false-positive nodes had severe anthracosis.
  • The authors suggested that severe anthracosis may be the main factor behind the FDG uptake in the false-positive nodes, rather than lymphoid follicular hyperplasia or histiocytic infiltration. They noted that these patients' workplaces suggested carbon dust exposure.
• The authors' conclusion: The authors concluded that, in patients with ARLC, FDG PET/CT had sensitivity and specificity comparable to those reported in the literature for conventional lung cancer. They found that many false-positive cases showed uptake on both sides of the chest, and said the method can be used to evaluate lymph node involvement in lung cancer.
• Limitations the authors state:
  • ARLC is rare and there were few false-positive lymph nodes, so further case series are needed to study their microscopic features.

Topics

Medical terms in this study, explained in our Lexicon: Intrathoracic, Lung Cancer, Metastasis, Surgical Resection, Bilateral, Anthracosis, CT Scan.

Related studies

• Asbestos content of lung tissue, lymph nodes, and pleural plaques from former shipyard workers — R.F. Dodson, M.G. Williams, et al. (1990)
• Intrapulmonary lymph nodes. Clinical, radiologic, and pathologic features — R.L. Kradin, P.W. Spirn, et al. (1985)
• Lymph node metastases in diffuse malignant peritoneal mesothelioma — D. Baratti, S. Kusamura, et al. (2010)
• Hyperplastic mesothelial cells in lymph nodes: report of six cases of a benign process that can stimulate metastatic involvement by mesothelioma or carcinoma — P. Argani, J. Rosai (1998)
• A comparison of asbestos burden in lung parenchyma, lymph nodes, and plaques — R.F. Dodson, M.G. Williams, et al. (1991)
• Asbestos content in the lymph nodes of nonoccupationally exposed individuals — R.F. Dodson, J. Huang, et al. (2000)

Browse more research in Journal of Thoracic Disease, or return to medical research.