Diffusion-Weighted Imaging Can Differentiate between Malignant and Benign Pleural Diseases

Our plain-English summary of Diffusion-Weighted Imaging Can Differentiate between Malignant and Benign Pleural Diseases, by K. Usuda, S. Iwai, A. Funasaki, et al (Cancers, 2019).

The study

• Authors: K. Usuda, S. Iwai, A. Funasaki, A. Sekimura, N. Motono, M. Matoba, M. Doai, S. Yamada, Y. Ueda, H. Uramoto
• Journal: Cancers
• Published: 2019;11(6)
• Cited by: 21 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

It is not clear whether magnetic resonance imaging (MRI) is useful for the assessment of pleural diseases. The aim of this study is to determine whether diffusion-weighted magnetic resonance imaging (DWI) can differentiate malignant pleural mesothelioma (MPM) from pleural dissemination of lung cancer, empyema or pleural effusion. The DWI was calibrated with the b value of 0 and 800 s/mm2. There were 11 MPMs (8 epithelioid and 3 biphasic), 10 pleural disseminations of lung cancer, 10 empyemas, and 12 pleural effusions. The apparent diffusion coefficient (ADC) of the pleural diseases was 1.22 ± 0.25 × 10-3 mm2/s in the MPMs, 1.31 ± 0.49 × 10-3 mm2/s in the pleural disseminations, 2.01 ± 0.45 × 10-3 mm2/s in the empyemas and 3.76 ± 0.62 × 10-3 mm2/s in the pleural effusions. The ADC of the MPMs and the pleural disseminations were significantly lower than the ADC of the empyemas and the pleural effusions. Concerning the diffusion pattern of DWI, all 11 MPMs showed strong continuous diffusion, 9 of 10 pleural disseminations showed strong scattered diffusion and 1 pleural dissemination showed strong continuous diffusion, all 10 empyemas showed weak continuous diffusion, and all 12 pleural effusions showed no decreased diffusion. DWI can evaluate pleural diseases morphologically and qualitatively, and thus differentiate between malignant and benign pleural diseases.

In plain English

This study from Kanazawa Medical University in Japan tested whether diffusion-weighted MRI (DWI), a scan that measures how freely water moves in tissue, could tell malignant pleural mesothelioma apart from other pleural diseases. Between March 2015 and February 2019, 43 patients had CT and MRI: 11 with mesothelioma (8 epithelioid, 3 biphasic), 10 with lung cancer spread to the pleura, 10 with empyema and 12 with pleural effusion. One effusion was attributed to asbestosis. Asbestos exposure itself was not studied. Average water-movement values (ADC, in units of 10−3 mm2/s) were 1.22 in mesotheliomas, 1.31 in lung cancer spread, 2.01 in empyemas and 3.76 in effusions. Both cancer groups had significantly lower values than empyemas and effusions, but mesothelioma did not differ significantly from lung cancer spread. The scan patterns did differ. All 11 mesotheliomas showed strong continuous diffusion, while 9 of 10 lung cancer cases showed strong scattered diffusion. The authors concluded that DWI can distinguish malignant from benign pleural diseases, and mesothelioma from pleural dissemination. They noted the study was small, done at a single institution, and open to selection bias.

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: Single-institution diagnostic imaging study comparing diffusion-weighted MRI findings across four groups of pleural disease
• Who was studied: 43 patients with pleural diseases or pleural effusions at Kanazawa Medical University, Japan, March 2015 to February 2019. The groups were 11 malignant pleural mesotheliomas (8 epithelioid, 3 biphasic), 10 pleural disseminations of lung cancer, 10 empyemas and 12 pleural effusions.
• Exposure: Asbestos exposure was not studied. No fiber types or exposure histories were reported. One of the 12 pleural effusions was attributed to asbestosis. The 'exposure' compared was the imaging test itself (DWI with b values of 0 and 800 s/mm2).
• Main results:
  • Mean ADC values (in 10−3 mm2/s, with standard deviations) were 1.22 ± 0.25 in mesotheliomas, 1.31 ± 0.49 in pleural disseminations of lung cancer, 2.01 ± 0.45 in empyemas and 3.76 ± 0.62 in pleural effusions.
  • ADC in mesotheliomas was significantly lower than in empyemas (P = 0.0007) and pleural effusions (P < 0.0001).
  • ADC in pleural disseminations of lung cancer was significantly lower than in empyemas (P = 0.0086) and pleural effusions (P < 0.0001).
  • ADC in mesotheliomas was not significantly different from ADC in pleural disseminations of lung cancer.
  • Diffusion patterns: all 11 mesotheliomas showed strong continuous diffusion; 9 of 10 pleural disseminations showed strong scattered diffusion and 1 showed strong continuous diffusion.
  • All 10 empyemas showed weak continuous diffusion and all 12 pleural effusions showed no decreased diffusion.
  • Among mesotheliomas, ADC in the 8 epithelioid cases (1.23 ± 0.26) was not significantly higher than in the 3 biphasic cases (1.17 ± 0.21), P = 0.73.
  • Among pleural disseminations of lung cancer, ADC in the 7 adenocarcinomas (1.63 ± 0.13) was significantly higher than in the 2 small cell carcinomas (0.68 ± 0.18), P = 0.0002.
  • ADC of the pleural fluid was significantly lower in empyemas (2.40 ± 1.26) than in mesotheliomas (P = 0.0023), pleural disseminations (P = 0.0286) and pleural effusions (P = 0.0009).
• The authors' conclusion: The authors concluded that DWI can evaluate pleural diseases morphologically and qualitatively, can differentiate malignant from benign pleural diseases, and can differentiate mesothelioma from pleural dissemination.
• Limitations the authors state:
  • The study was done at a single institution with a small number of patients, which the authors said introduced selection bias.
  • Consent forms could not be obtained from all patients who developed pleural lesions during the study period, which kept the sample small.
  • The recorded ADC was the minimum of three measurements and may not fully represent the whole tumor.
  • There is no agreement in the literature on optimal DWI techniques and image analysis, including region-of-interest size and placement.
  • The small sample did not allow the authors to repeat an earlier study's finding of an ADC difference between epithelioid and biphasic mesothelioma.
  • Some benign conditions (pulmonary abscesses and empyemas with necrosis) can show decreased diffusion and lower ADC values.
  • Mucinous adenocarcinomas can show higher ADC values and could be misjudged as benign.

Topics

Medical terms in this study, explained in our Lexicon: Pleural Mesothelioma, Lung Cancer, Empyema, Pleural Effusion, Epithelioid, Biphasic Mesothelioma.

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• Diffusion-weighted MRI of malignant pleural mesothelioma: preliminary assessment of apparent diffusion coefficient in histologic subtypes — R.R. Gill, S. Umeoka, et al. (2010)
• Accelerating Whole-Body Diffusion-weighted MRI with Deep Learning-based Denoising Image Filters — K. Zormpas-Petridis, N. Tunariu, et al. (2021)
• Diffusion magnetic resonance imaging of chest tumors — A.A. Razek (2012)
• Molecular markers and new diagnostic methods to differentiate malignant from benign mesothelial pleural proliferations: a literature review — R. Bruno, G. Alì, et al. (2018)

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