Smoking-associated fibrosis and pulmonary asbestosis

Our plain-English summary of Smoking-associated fibrosis and pulmonary asbestosis, by J.R. Bledsoe, D.C. Christiani, R.L. Kradin (International Journal of Chronic Obstructive Pulmonary Disease, 2015).

The study

• Authors: J.R. Bledsoe, D.C. Christiani, R.L. Kradin
• Journal: International Journal of Chronic Obstructive Pulmonary Disease
• Published: 2015;10:31-7
• Cited by: 10 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

The diagnosis of pulmonary asbestosis is most often established based on clinical criteria and has both clinical and legal implications. Unfortunately, one of the confounding features in the diagnosis may be a history of cigarette abuse, which can produce interstitial opacities on chest imaging as well as diffusion defects on pulmonary function testing, criteria that are used in the diagnosis of pulmonary asbestosis. The objective of the present study was to evaluate the correlation of radiographically detected pulmonary fibrosis with fibrosis established histopathologically as attributable to asbestos, in a cohort referred for diagnosis of an asbestos-related malignancy in the context of litigation. We examined the slides of 186 cases with reported asbestos exposure, referred in consultation for asbestos-related malignancy and the presence of pulmonary fibrosis. Sixty-five cases had what was judged to be adequate tissue sampling for histopathologic evaluation of asbestosis as well as an existing radiologic assessment of pulmonary fibrosis by B-reader report. Of 24 cases judged to have asbestosis radiographically, which had sufficient tissue for pathologic examination, six showed asbestosis histopathologically. The remaining 18 cases (mean smoking history of 53 pack-years) showed interstitial fibrosis that was judged to be most consistent with smoking-associated pulmonary fibrosis. We conclude that the clinical diagnosis of mild asbestosis cannot be reliably distinguished from interstitial fibrosis in heavy smokers.

In plain English

The authors reviewed the medical records, B-reader chest X-ray reports and lung tissue slides of 186 people from across the United States who were referred, in the context of litigation, for an opinion on asbestos-related disease. Of these, 101 had lung cancer and 77 had malignant mesothelioma. Asbestos exposure, mostly occupational, was self-reported, and 126 of 143 people with smoking data were smokers. B readers had made a radiographic diagnosis of asbestosis in 62 of 183 cases. Of 67 cases with enough lung tissue showing fibrosis, 24 had been called asbestosis on exposure and X-ray grounds. Under the microscope, 6 of these 24 showed asbestosis. The other 18 showed scarring that the authors judged characteristic of smoking-associated fibrosis, with no asbestos bodies; 16 of them were known smokers averaging 53 pack-years. The authors concluded that an X-ray finding of mild asbestosis in heavy smokers should be viewed with skepticism. They listed several limitations: a small sample, the litigation setting, B readings that were not confirmed, unblinded review and no unexposed controls. They also said a contribution from asbestos could not be entirely ruled out.

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 review of consecutive consultation cases (records, B-reader reports and pathology slides), not prospective, without controls
• Who was studied: 186 consecutive consultation cases (174 men, 12 women, average age 68) referred from throughout the United States to one author's practice for assessment of asbestos-related disease in litigation. 178 had a malignancy.
• Exposure: Self-reported asbestos exposure, primarily occupational (trades such as laborer, plumber/pipefitter, shipyard, electrician). All but one woman reported secondary exposure from laundering husbands' work clothes. Average duration of putative exposure was 27 years. No information on specific products, and no fiber type is given. Cigarette smoking averaged 46 pack-years among those with data.
• Main results:
  • Malignancy in the whole cohort: 101 (54%) had a primary lung cancer and 77 (41%) had malignant mesothelioma.
  • Radiographic diagnosis of asbestosis (ILO profusion 1/0 or 1/1) in 62 (34%) of the 183 cases with B-reader reports.
  • Of the 67 cases with tissue sufficient for evaluation, 24 had been diagnosed as asbestosis on exposure and radiographic grounds.
  • Of those 24 cases, 6 (25%) had asbestosis confirmed on histopathology, and all 6 had an ILO profusion of 1/1.
  • The remaining 18 of the 24 showed scarring characteristic of smoking-associated fibrosis with no asbestos bodies seen. 16 had a definite smoking history (mean 53 pack-years) and 2 had no smoking data.
  • Histopathologic evidence of asbestosis was found in 12% of evaluable cases (8 of 67), compared with a clinical/radiographic diagnosis in 34%.
• The authors' conclusion: The authors concluded that a radiographic finding of mild asbestosis in a person with a history of heavy smoking should be viewed with skepticism. In their view, an ILO reading at the 1/0 threshold indicated mild interstitial lung disease but lacked specificity. They called for prospective controlled studies.
• Limitations the authors state:
  • Small sample: 65 cases with both pathologic and radiologic diagnoses, and 24 with radiology consistent with asbestosis plus adequate tissue.
  • The study was not prospective, the cases came from litigation, and the B readings were not independently confirmed.
  • Possible litigation bias.
  • Pathology review was not blinded to exposure, smoking or B readings, and no unexposed controls were used.
  • Fiber analysis was not done because lung tissue was not available.
  • In cases with fibrosis but no asbestos bodies, an influence of asbestos cannot be entirely ruled out. The authors noted that products such as chrysotile can cause fibrosis without significant asbestos body formation.
  • No epidemiological studies have yet definitively proven that smoking causes this fibrosis.

Topics

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

Medical terms in this study, explained in our Lexicon: Fibrosis, Asbestosis, Confounding, Interstitial, Pulmonary Fibrosis, Asbestos Exposure, B-Reader, Interstitial Fibrosis.

Related studies

• Asbestosis: interstitial pulmonary fibrosis and pleural fibrosis in a cohort of asbestos insulation workers: influence of cigarette smoking — R. Lilis, I.J. Selikoff, et al. (1986)
• Interaction of asbestos, age, and cigarette smoking in producing radiographic evidence of diffuse pulmonary fibrosis — K.H. Kilburn, R. Lilis, et al. (1986)
• Cigarette smoking, asbestos, and pulmonary fibrosis — W. Weiss (1971)
• Cigarette smoking does not produce or enhance the radiologic appearance of pulmonary fibrosis — K.H. Kilburn (1981)
• Pulmonary function, smoking habits, and high resolution computed tomography (HRCT) early abnormalities of lung and pleural fibrosis in shipyard workers exposed to asbestos — S. Neri, P. Boraschi, et al. (1996)
• Radiological characteristics, histological features and clinical outcomes of lung cancer patients with coexistent idiopathic pulmonary fibrosis — K.A. Khan, M.P. Kennedy, et al. (2015)

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