Mortality in cases of asbestosis diagnosed by a pneumoconiosis medical panel

Our plain-English summary of Mortality in cases of asbestosis diagnosed by a pneumoconiosis medical panel, by I.I. Coutts, J.C. Gilson, I.H. Kerr, et al (Thorax, 1987).

The study

• Authors: I.I. Coutts, J.C. Gilson, I.H. Kerr, W.R. Parkes, M. Turner-Warwick
• Journal: Thorax
• Published: 1987;42(2):111-6
• Cited by: 19 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text
• In J-M's library: Johns-Manville's company medical library held a copy (J-M no. 000956).

Abstract

One hundred and fifty five male cases of asbestosis certified by the London Pneumoconiosis Medical Panel during 1968-74 were followed up during 1978-9, 4-11 (mean 7.5) years after certification. Fifty nine patients had died, 23 (39%) from lung cancer, 6 (10%) from mesothelioma, and 11 (19%) from other respiratory causes. The number of observed deaths was 2.25 times greater than expected and 7.4 times greater than expected for lung cancer. Adenocarcinoma was the commonest histological type but other cell types were also increased. Finger clubbing (p less than 0.01) and percentage of predicted FEV1 (p less than 0.01) were of value in predicting death, but increasing profusion of small opacities greater than 1/0 (ILO/U-C international classification of radiographs of pneumoconiosis, 1971), duration of exposure to asbestos, time from first exposure to asbestos, and percentage of predicted vital capacity and transfer factor did not predict death.

In plain English

The authors followed 155 men diagnosed with asbestosis by the London Pneumoconiosis Medical Panel from 1968 to the end of 1974. By the end of August 1979, 59 had died. Of these deaths, 26 (44%) involved lung cancer, 6 were from mesothelioma and 11 were from other respiratory causes. Over the 10 years after certification, deaths were 2.26 times the number expected from England and Wales life tables. Lung cancer deaths were 7.4 times the expected number on death certificate data (8.4 times on panel information). Adenocarcinoma was the most common lung cancer type (41%). Finger clubbing, age and a lower FEV1 (a breathing test) at presentation helped separate the men who died from the survivors. Among men with X-ray signs of fibrosis, the extent of those signs did not predict death, and neither did length of exposure or time since first exposure. The 36 men with category 0 X-rays had no overall excess of deaths but more lung cancer deaths than expected (3 observed, 0.74 expected). Smoking could not be studied because only five men had never smoked. The authors suggested that, once certifiable asbestosis develops, life expectancy may be relatively independent of asbestos dose.

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: Mortality follow-up of men certified as having asbestosis. Observed deaths were compared with expected deaths, calculated by the subject-years-at-risk method using England and Wales life tables for 1970-72. A discriminant analysis looked for features at first examination that predicted death.
• Who was studied: 155 men diagnosed with asbestosis by the London Pneumoconiosis Medical Panel. They were seen from 1968 to the end of 1974 and had respiratory function tests at the Brompton Hospital, London. They were followed to the end of August 1979.
• Exposure: Asbestos exposure; the article does not name fiber types. The authors describe the men as heavily exposed workers. Many had worked in a factory previously studied by Newhouse, and many were laggers. Duration of exposure and time since first exposure were examined as possible predictors.
• Main results:
  • 59 of the 155 men had died by the end of August 1979.
  • Lung cancer was present in 26 (44%) of the 59 deaths. It appeared on the death certificate in only 23 (39%) of them.
  • Overall mortality in the 10 years after certification was 2.26 times greater than expected.
  • There was excess mortality at five and 10 years (p less than 0.001). It was due to excess deaths from lung cancer (p less than 0.001), respiratory disease (p less than 0.001) and mesothelioma.
  • For lung cancer, the ratio of observed to expected deaths was 7.4 using death certificate data and 8.4 using panel information.
  • There were six mesothelioma deaths in 1107 man-years of observation. The authors called this clearly excessive for a rare disease.
  • Eleven men died from respiratory causes other than lung cancer or mesothelioma.
  • No deaths from laryngeal cancer occurred.
  • No excess of gastrointestinal cancer was found.
  • 36 men were certified with a category 0 chest radiograph. This group had no overall excess mortality, but lung cancer mortality was significantly increased (3 observed, 0.74 expected, p less than 0.03).
  • Among men with radiographic evidence of fibrosis, the severity of asbestosis as scored by profusion of small opacities did not predict outcome.
  • In the discriminant analysis, finger clubbing (p less than 0.05) and age (p less than 0.025) helped distinguish survivors from non-survivors. Percentage of predicted FEV1 also helped.
  • Mean percentage of predicted FEV1 at presentation was 72.3% (SD 17.3) in survivors and 64.5% (SD 18.3) in non-survivors.
  • The discriminant function misclassified an estimated 28% of cases.
  • Neither duration of exposure nor time from first exposure predicted death.
  • Among the 26 men with lung cancer (27 tumours, since one man had two primary tumours), adenocarcinoma was the most common type: 11 tumours, 41%. The others were 9 squamous cell, 4 oat cell, 1 undifferentiated and 2 unknown.
  • Adenocarcinoma accounted for four of the five tumours in lungs with the most severe radiographic fibrosis (categories 2 and 3).
• The authors' conclusion: The authors concluded that, given enough asbestos exposure to develop certifiable asbestosis, life expectancy may be relatively independent of the dose of inhaled asbestos and of the radiographic severity of fibrosis.
• Limitations the authors state:
  • The effect of cigarette smoking could not be studied, because only five of the 155 men had never smoked.
  • The exposure data were crude and could have obscured a real relationship with mortality.
  • Claimants before a pneumoconiosis medical panel are a highly selected group, which may partly explain the mortality pattern seen.
  • Laryngeal cancer is rare, and a small study could easily miss an excess.
  • It is uncertain whether adenocarcinoma is truly increased in asbestosis, because there was no comparable series of lung cancers without asbestos exposure.

Topics

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

Medical terms in this study, explained in our Lexicon: Pneumoconiosis, Lung Cancer, Mesothelioma, Adenocarcinoma, Clubbing, FEV1.

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