Potential asbestos exposure among patients with primary lung cancer in Japan

Our plain-English summary of Potential asbestos exposure among patients with primary lung cancer in Japan, by A. Tamura, M. Funakoshi, N.A. J-P, et al (Journal of Occupational Health, 2018).

The study

• Authors: A. Tamura, M. Funakoshi, N.A. J-P, K. Hasegawa, A. Ishimine, A. Koike, N. Tannai, M. Fujii, M. Hattori, H. Hirano, K. Nakamura, M. Funakoshi, K. Satomi, Y. Yamashita, Y. Fukuchi, N. Suganuma
• Journal: Journal of Occupational Health
• Published: 2018;60(3):236-245
• Cited by: 16 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Objective: To investigate the extent of asbestos exposure among patients with primary lung cancer in Japan.

Methods: A retrospective estimation of potential asbestos-exposed individuals, as determined by the presence of pleural plaques identified on chest computed tomography (CT), was conducted on 885 pathologically confirmed primary lung cancer patients (mean age 71.3 years, 641 males). All patients were diagnosed at 29 hospitals across Japan between 2006 and 2007. Since these hospitals belong to the Japan Federation of Democratic Medical Institutions (MIN-IREN), an organization of medical institutions for workers, the study subjects may contain a higher proportion of workers than the general population.

Results: Pleural plaques were identified in 12.8% of subjects (15.8% in males and 4.9% in females), consisting exclusively of cases older than 50 years. They were found most frequently on the chest wall pleura (96.5%), followed by the diaphragm (23.9%) and mediastinum (9.7%). Calcifications were seen in 47 cases (41.6%). The highest prevalence of pleural plaques was seen among workers from construction-related fields (37.7%). No distinct lung cancer histology was observed in patients with pleural plaques. Coexistence of pleural plaques and small irregular opacities was observed in 2.5% of subjects.

Conclusion: In a Japanese population representing more workers than general Japanese, 12.8% of patients with primary lung cancer may have experienced asbestos exposure at some time in the past. Special medical attention should be paid to individuals with a history of employment in construction-related occupations, as workers in this sector showed the highest prevalence of pleural plaques.

In plain English

This study reviewed records of 885 patients diagnosed with primary lung cancer in 2006 and 2007 at 29 Japanese hospitals. The hospitals belong to MIN-IREN, a federation serving workers, so the authors noted their patients may include more workers than the general population. Experts reviewed chest CT scans for pleural plaques, which the authors used as a sign of past asbestos exposure. No fiber types or doses were measured. Plaques were found on CT in 113 patients (12.8%): 15.8% of males and 4.9% of females, and none under 50. Among major job categories, plaques were most frequent in security workers (4 of 9, 44.4%), a group the authors called too small for meaningful conclusions, and in manufacturing and general laborers (52 of 215, 24.2%). Within the latter's subgroups with more than 10 patients, construction-related workers ranked highest (37.7%). Cell types did not differ clearly by plaque status. The authors concluded that 12.8% of these patients may have been exposed to asbestos in the past. They stated they could not establish that asbestos caused these cancers, and that strict criteria may have underestimated plaques.

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 hospital-based multicenter study (review of medical records and chest images)
• Who was studied: 885 consecutive patients (641 males, 244 females, ages 26 to 94) with histologically or cytologically confirmed primary lung cancer, diagnosed between January 1, 2006 and December 31, 2007 at 29 MIN-IREN hospitals in 19 prefectures of Japan. Of 947 cases initially obtained, 62 were excluded because their chest images could not be interpreted.
• Exposure: Asbestos exposure was not measured directly. CT-confirmed pleural plaques (parietal type, rated 'definite' or 'probable') were used as a surrogate for past asbestos exposure. Occupation was taken from medical charts for 615 cases and grouped by the Japanese ESCO classification. No fiber types are specified.
• Main results:
  • Pleural plaques were found on chest CT in 113 of 885 patients (12.8%). Of 125 cases with pleural abnormalities on CT, 12 with changes mainly in the visceral pleura were excluded.
  • Plaques were found in 15.8% of males (101) and 4.9% of females (12). No patient aged 49 or younger had plaques.
  • Chest X-rays identified plaques in 48 cases (5.4%). CT and X-ray agreed on 38 cases (4.3%). Of the 48 X-ray-positive cases, 10 were found on CT to have other causes.
  • Among the 113 patients with plaques, the chest wall pleura was involved in 109 (96.5%), the diaphragm in 27 (23.9%) and the mediastinum in 11 (9.7%). Plaques were calcified in 47 (41.6%), and irregular opacities coexisted in 22 (19.5%).
  • Among the major occupational categories (615 patients with a recorded occupation), plaque prevalence was highest among security workers (4 of 9, 44.4%), manufacturing and general laborers (52 of 215, 24.2%), and transport and communication workers (5 of 36, 13.9%). The denominators are the category totals in Table 5. The authors said the small numbers in the security and transport groups make meaningful conclusions difficult.
  • Within manufacturing and general labor subcategories with more than 10 lung cancer patients, prevalence was highest in construction-related workers (37.7%), followed by metal processing (26.7%), civil construction laborers (26.7%), foundry workers (23.5%), miners (22.2%) and electricians (21.4%).
  • Plaque prevalence was 15.3% among ever-smokers and 9% among non-smokers (among the 692 patients with smoking information).
  • The distribution of lung cancer cell types did not differ distinctly between patients with and without plaques (p = .768 in the table).
• The authors' conclusion: The authors concluded that 12.8% of these primary lung cancer patients had pleural plaques on CT and may have had past asbestos exposure, with the highest frequency among people with construction-related employment. They stated they cannot postulate a causal relationship between asbestos exposure and lung cancer in these cases, and that results must be interpreted cautiously.
• Limitations the authors state:
  • The patients came from hospitals that serve workers, so they may include more workers, and more asbestos-exposed people, than the general Japanese population.
  • The strict CT definition may have underestimated the true proportion of plaques and asbestos exposure.
  • CT could have missed some plaques, and the absence of plaques does not necessarily rule out past asbestos exposure.
  • Because the study was retrospective, occupational information was limited.
  • Small numbers of security and transport and communication workers make conclusions about those groups difficult.
  • The study could not separate the contributions of asbestos, other carcinogens and smoking (74.4% of patients were ever-smokers) to the development of lung cancer.

Topics

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

Medical terms in this study, explained in our Lexicon: Asbestos Exposure, Lung Cancer, Pleural Plaques, Pleura, Diaphragm, Mediastinum, Histology.

Related studies

• The prevalence of pleural plaques and/or pulmonary changes among construction workers in Okayama, Japan — T. Kishimoto, K. Morinaga, et al. (2000)
• Railways and asbestos in Japan (1928-1987)--epidemiology of pleural plaques, malignancies and pneumoconioses- — Y. Hosoda, Y. Hiraga, et al. (2008)
• Fatal pleural mesothelioma in Japan (2003-2008): evaluation of computed tomography findings — K. Kato, K. Gemba, et al. (2016)
• Asbestos-related diffuse pleural thickening — N. Fujimoto, K. Kato, et al. (2014)
• A case-control study on occupational lung cancer risks in an industrialized city of Japan — N. Yamaguchi, M. Kido, et al. (1992)
• Work environment of plants manufacturing asbestos-containing products in Japan — T. Higashi, H. Hori, et al. (1994)

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