Evidence for longer survival of patients with pleural mesothelioma without asbestos exposure

Our plain-English summary of Evidence for longer survival of patients with pleural mesothelioma without asbestos exposure, by M.R. Law, F.G. Ward, M.E. Hodson, et al (Thorax, 1983).

The study

• Authors: M.R. Law, F.G. Ward, M.E. Hodson, B.E. Heard
• Journal: Thorax
• Published: 1983;38(10):744-6
• Cited by: 24 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. 001751).

Abstract

In a group of 23 patients with histologically confirmed malignant mesothelioma of the pleura who could not recall exposure to asbestos dust, survival was significantly longer than in a group of 83 patients with known exposure. Asbestos bodies were found by a quantitative method significantly less frequently in the unexposed than in the exposed group. The longer survival of patients without known exposure could not be correlated with any significant difference in the histological cell types of the tumours from those of exposed patients. In the 83 patients with known exposure survival did not relate to duration of exposure. Consequently, although the tumours of patients unable to recall exposure may be caused by unrecognised environmental contamination with asbestos dust, the longer survival of these patients would suggest a different aetiology.

In plain English

This study, from the Brompton Hospital and Cardiothoracic Institute in London, compared patients with malignant mesothelioma of the pleura who did and did not have a history of asbestos dust exposure. Of a series of 115 cases whose tissue had been re-examined, 83 had a clearly documented history of exposure, 23 could not recall exposure despite close questioning, and 9 were inadequately documented. Survival from first symptoms was significantly longer in the 23 patients who could not recall exposure (median 25 months) than in the 83 exposed patients (median 15 months). The exposed group had a significantly higher proportion of men, but the survival difference remained when only men were examined. Age, clinical features and tumour cell types did not differ significantly between the groups. Among exposed patients, survival did not differ significantly by duration of exposure. In lung tissue taken after death, asbestos bodies were found significantly less often in the 11 unexposed cases examined than in exposed cases. The authors concluded that the longer survival of patients unable to recall exposure suggests a different cause. They noted that histological confirmation of the diagnosis sometimes came late in the disease.

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: Comparison within a hospital case series of pleural mesothelioma patients, grouped by whether asbestos exposure was documented or not recalled. Survival was compared using actuarial survival curves, and asbestos bodies were counted in postmortem lung tissue.
• Who was studied: 115 cases of histologically confirmed malignant pleural mesothelioma from the Brompton and London Chest Hospitals. 83 had a clear history of asbestos exposure (73 men and 10 women), 23 could not recall exposure (13 men and 10 women), and 9 had inadequately documented exposure (8 men and 1 woman). Postmortem lung tissue was available for 67 exposed and 11 unexposed cases.
• Exposure: Asbestos dust exposure as recorded in the clinical history; fiber types were not stated. Exposed patients were subdivided into direct occupational exposure lasting less than 1 year, 1 to 5 years, or more than 5 years, and indirect exposure (indirect occupational, paraoccupational and neighbourhood).
• Main results:
  • Survival from first symptoms to death was significantly longer for the 23 patients who could not recall exposure than for the 83 with known exposure (p less than 0.01 at 12 months and thereafter). Median survival from first symptoms was 25 months in the unexposed group, 15 months in the exposed group and 16 months in the inadequately documented group.
  • Survival also differed significantly from the time of hospital referral and from the time of diagnosis. Median survival from diagnosis was 19 months in the unexposed group, 10 months in the exposed group and 12 months in the inadequately documented group.
  • There was a significantly higher proportion of men among the 83 exposed patients (73 of 83) than among the 23 unable to recall exposure (13 of 23), p less than 0.01. Sex did not significantly affect survival within either group.
  • The survival difference between patients with and without known exposure remained when men alone were examined.
  • There were no significant differences in clinical features, age, or distribution of histological types (epithelial, mixed, sarcomatous) between patients with and without known exposure. For example, epithelial tumours made up 51% of the exposed group and 52% of the unexposed group.
  • Among exposed patients, survival from first symptoms did not differ significantly by duration of direct occupational exposure or for indirect exposure.
  • Asbestos bodies were found significantly less often in lung tissue from patients who could not recall exposure than in any of the four exposed categories (p less than 0.05, Fisher's exact test). Of the 11 unexposed cases, 8 had none, 3 had occasional and 0 had numerous asbestos bodies. Of the 24 cases with more than 5 years' exposure, 16 had numerous bodies.
  • The proportion of cases with numerous asbestos bodies rose significantly with increasing duration of exposure. The proportion with any asbestos bodies showed a similar significant increasing trend.
• The authors' conclusion: The authors stated it is not certain whether mesothelioma in patients unable to recall exposure is caused by small amounts of household or other environmental asbestos dust. They concluded that the longer survival of these patients suggests a different aetiology, since survival was not related to duration of exposure among exposed patients.
• Limitations the authors state:
  • Histological confirmation of the diagnosis was sometimes made late in the disease, and in 10 cases was deferred until autopsy. This bears on survival measured from diagnosis.

Topics

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

Medical terms in this study, explained in our Lexicon: Pleural Mesothelioma, Asbestos Exposure, Mesothelioma, Pleura, Asbestos Bodies.

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