Fatal pleural mesothelioma in Japan (2003-2008): evaluation of computed tomography findings

Our plain-English summary of Fatal pleural mesothelioma in Japan (2003-2008): evaluation of computed tomography findings, by K. Kato, K. Gemba, N. Fujimoto, et al (Japanese Journal of Radiology, 2016).

The study

• Authors: K. Kato, K. Gemba, N. Fujimoto, K. Aoe, Y. Takeshima, K. Inai, T. Kishimoto
• Journal: Japanese Journal of Radiology
• Published: 2016;34(6):432-8
• Cited by: 4 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Purpose: The purpose of this study was to clarify the characteristic findings of mesothelioma at the time of diagnosis, and determine precautions and guidelines for diagnosing mesothelioma early in imaging studies.

Materials And Methods: Overall, 327 patients with pleural mesothelioma were selected from 6030 patients who died of mesothelioma between 2003 and 2008 in Japan. Their imaging findings were examined retrospectively.

Results: Plaques were found in 35 % of computed tomography (CT) scans. Asbestosis, diffuse pleural thickening, and rounded atelectasis were found in only seven (2 %), five (2 %), and two cases (1 %), respectively. Pleural thickening findings on CT scans were classified into four stages: no irregularity, mild irregularity, high irregularity, and mass formation. Overall, 18 % of cases did not show a clear irregularity. Localized thickening was observed in the mediastinal (77 %) and basal (76 %) pleura and in the interlobar fissure (49 %). Eight percent of cases did not have any thickening in these three areas.

Conclusions: Upon examination of the CT scans at diagnosis, 18 % of mesothelioma cases did not show a clear irregularity. When diagnosing pleural effusion of unknown etiology, it is necessary to consider the possibility of mesothelioma even when no plaque and pleural irregularity are observed.

In plain English

This retrospective study reviewed CT scans of people in Japan who died of pleural mesothelioma. National death records listed 6030 mesothelioma deaths in 2003–2008. Through relatives' consent and hospital records, the authors reached 327 pleural mesothelioma patients whose chest CT scans at diagnosis were reviewed jointly by three experienced physicians. Pleural plaques were seen on CT in 114 of 327 patients (35%) but on plain chest X-rays in 36 (11%). Pleural effusion (fluid around the lung) was found in 304 (93%). Asbestosis, diffuse pleural thickening and rounded atelectasis each appeared in 2% or fewer. When pleural changes were graded, 7 cases (2%) showed no irregularity and 53 (16%) only mild irregularity, so 18% lacked changes suggesting cancer; all 7 and 49 of the 53 were in the low tumor (T) category T1–2. Lesions were most often in the mediastinal pleura (77%). CT findings were not significantly linked to tumor subtype. The authors concluded that mesothelioma should be considered in unexplained pleural effusion even without plaques or pleural irregularity. They noted limits: varied scanners, differing diagnostic timing between hospitals, and no check of reader agreement.

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 nationwide survey; review of CT and plain chest X-ray images taken at diagnosis in patients who later died of pleural mesothelioma
• Who was studied: 327 patients with pleural mesothelioma (273 men, 54 women; mean age 68) who had chest CT images taken at diagnosis. They were drawn from 6030 people recorded in Japan's Vital Statistics as having died of mesothelioma between 2003 and 2008. Relatives of 2069 consented, data came back for 1111, the diagnosis was confirmed in 929, and 794 of those had pleural mesothelioma.
• Exposure: Asbestos exposure was not measured in this study. The authors state that the national sample included both people who did not work with asbestos and people who worked in asbestos-related industries.
• Main results:
  • Pleural plaque was seen on CT in 114 of 327 patients (35%), and 56 of those (49%) had calcification. Plain chest X-rays showed plaque in only 36 of 327 patients (11%).
  • Pleural effusion was found in 304 patients (93%). Lung asbestosis was found in 7 patients (2%), diffuse pleural thickening in 5 (2%) and rounded atelectasis in 2 (1%).
  • The 327 cases were graded by pleural thickening. 7 showed no irregularity (2%), 53 mild irregularity (16%), 140 high irregularity (43%) and 127 mass formation (39% in Table 1). Overall, 82% had irregularities suggesting possible cancer and 18% did not.
  • All 7 cases with no irregularity were in tumor (T) category T1–2, as were 49 (92%) of the cases with mild irregularity. Among cases with high irregularity, 78% were T3–4, and among cases with mass formation, 84% were T3–4.
  • Lesions were found in the mediastinal pleura in 251 patients (77%), at the base of the lungs in 250 (76%) and in the interlobular pleura in 159 (49%). The results section states that 27 cases (8%) had no lesions in the mediastinal and interlobular pleurae.
  • There was no statistically significant correlation between the CT findings and the pathological subtype (epithelial versus non-epithelial).
• The authors' conclusion: The authors concluded that 18% of the mesothelioma cases did not show a clear irregularity on CT and were classified as low T-stage at diagnosis. They said that when diagnosing pleural effusion of unknown cause, pleural mesothelioma must be considered even without identifiable plaque. They added that slight changes in the mediastinal or interlobar pleura can raise suspicion. Given the low rates of asbestosis and plaque, they also stated their belief that few of these cases had high-concentration asbestos exposure.
• Limitations the authors state:
  • The study was retrospective, and cases came from many institutions using a variety of CT and X-ray devices and methods.
  • Diagnostic ability and the timing of diagnosis varied between hospitals, which may have introduced bias.
  • Variation between the image readers (interobserver variation) was not evaluated.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Lung cancer, Mesothelioma.

Medical terms in this study, explained in our Lexicon: Pleural Mesothelioma, Mesothelioma, Diffuse Pleural Thickening, Rounded Atelectasis, Pleural Thickening, CT Scan, Pleura, Pleural Effusion.

Related studies

• National survey of malignant mesothelioma and asbestos exposure in Japan — K. Gemba, N. Fujimoto, et al. (2012)
• Computed tomography findings in 66 patients with malignant pleural mesothelioma due to environmental exposure to asbestos — F. Okten, D. Köksal, et al. (2006)
• Treatment and survival analyses of malignant mesothelioma in Japan — K. Gemba, N. Fujimoto, et al. (2013)
• Low-dose chest computed tomography screening of subjects exposed to asbestos — K. Kato, K. Gemba, et al. (2018)
• Pleural irregularities and mediastinal pleural involvement in early stages of malignant pleural mesothelioma and benign asbestos pleural effusion — K. Kato, K. Gemba, et al. (2016)
• Findings from high resolution computed tomography of the lung and pleura of symptom free workers exposed to amosite who had normal chest radiographs and pulmonary function tests — S. Neri, A. Antonelli, et al. (1994)

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