Is pleural infection associated with longer survival in mesothelioma? A population-based cohort study using data from Hospital Episode Statistics

Our plain-English summary of Is pleural infection associated with longer survival in mesothelioma? A population-based cohort study using data from Hospital Episode Statistics, by A.C. Bibby, D. de Fonseka, D.J. Carslake, et al (Cancer Epidemiology, 2019).

The study

• Authors: A.C. Bibby, D. de Fonseka, D.J. Carslake, N.A. Maskell
• Journal: Cancer Epidemiology
• Published: 2019;59:75-82
• Cited by: 1 article, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Background: Historically pleural infection was thought to be associated with longer survival in thoracic malignancies. The aim of this population-based cohort study was to investigate this hypothesis in mesothelioma, using national data from a high incidence country.

Methods: Case records for all patients with mesothelioma seen in English hospitals between 01/01/2005 and 31/12/2014 were extracted from Hospital Episode Statistics using International Classification of Diseases Tenth Edition (ICD-10) codes. Episodes of pleural infection were identified. Linked mortality data was obtained from the Office of National Statistics. The primary outcome was all-cause mortality. The explanatory variable was pleural infection. Cox proportional hazards model was used to analyse survival, with pleural infection, chemotherapy and thoracic surgery handled as time-variable co-factors.

Results: Of 22,215 patients with mesothelioma, 512 (2.3%) developed pleural infection at some point in their illness. Overall median survival was 7.0 months (IQR 2.3-16.4). Pleural infection was associated with shorter survival in the immediate post-infection period (up to 30 days - HR 1.81, 95% CI 1.45-2.22) and longer term (>30 days - HR 1.81, 95% CI 1.63-1.99). Other factors associated with increased mortality were age, male gender and being diagnosed as an inpatient. Receiving chemotherapy and being less economically deprived were associated with longer survival.

Conclusion: Pleural infection occurred in 2.3% of people with mesothelioma and was associated with shorter survival. This refutes previous reports suggesting pleural infection may be associated with better outcomes in thoracic malignancy.

Copyright © 2019. Published by Elsevier Ltd.

In plain English

This population-based cohort study used English hospital records linked to national death records. It tested an older idea that pleural infection might lengthen survival in mesothelioma. It included 22,215 mesothelioma patients seen in English hospitals from 2005 to 2014, of whom 512 (2.3%) developed pleural infection. Median survival for the whole group was 7.0 months. After adjustment for other factors, death rates were higher after pleural infection: hazard ratio 1.81 in the first 30 days (95% CI 1.47 to 2.22 in the table; 1.45 to 2.22 in the abstract) and 1.81 beyond 30 days (95% CI 1.63 to 1.99). Older age, male sex and inpatient diagnosis were also linked to higher mortality. Receiving chemotherapy and being less economically deprived were linked to longer survival. Documented asbestos exposure and pleural plaques were each associated with slightly higher mortality. The authors concluded that pleural infection was associated with shorter survival, contrary to earlier reports. They noted that this observational study cannot show cause, that dying patients may be more likely to develop infection, and that performance status, tumour type and infecting bacteria were not recorded.

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: Population-based cohort study using historic national hospital and death-registration data. Survival was analysed with Cox proportional hazards models, with pleural infection treated as a time-varying factor.
• Who was studied: 22,215 patients with mesothelioma (out of 22,896 records identified) who attended English hospitals between 1 January 2005 and 31 December 2014. They were 81.7% male, with mean age 71.8 years. Disease site was 51.5% pleural, 5.0% peritoneal and 0.4% pericardial, and not specified in 42.9%.
• Exposure: The exposure studied was pleural infection, identified by ICD-10 codes J86, J86.0 and J86.9. Documented asbestos exposure and pleural plaques were included only as adjustment factors, and no fiber types were reported.
• Main results:
  • 512 of 22,215 patients with mesothelioma (2.3%) developed pleural infection.
  • Pleural infection incidence was highest in the first 30 days after mesothelioma diagnosis, at 170.0 per 1000 patient-years (95% CI 151.4 to 190.9). It fell to 33.9 per 1000 patient-years for days 31 to 90, and to 6.5 per 1000 patient-years after 90 days.
  • Median survival was 6.2 months in patients with pleural infection, compared with 7.0 months in those without (unadjusted HR 1.12, 95% CI 1.02 to 1.22).
  • In the first 30 days after pleural infection, adjusted all-cause mortality was higher than before or without infection, with HR 1.81. The 95% CI is 1.47 to 2.22 in Table 3 and 1.45 to 2.22 in the abstract.
  • More than 30 days after pleural infection, adjusted all-cause mortality was also higher, with HR 1.81 (95% CI 1.63 to 1.99).
  • In the whole cohort, older age, male gender and being diagnosed as an inpatient were associated with higher mortality.
  • Receiving chemotherapy (adjusted HR 0.96, 95% CI 0.93 to 0.99) and lower economic deprivation were associated with longer survival.
  • Documented asbestos exposure (adjusted HR 1.07, 95% CI 1.03 to 1.12) and documented pleural plaques (adjusted HR 1.11, 95% CI 1.05 to 1.18) were associated with higher all-cause mortality.
  • Most patients (18,604 of 22,215; 84%) died of mesothelioma, so results for mesothelioma-specific mortality were similar to the main analysis.
• The authors' conclusion: The authors concluded that in this national cohort, pleural infection was associated with higher 30-day and long-term mortality. They stated that this refutes earlier hypotheses that pleural infection is associated with longer survival in mesothelioma.
• Limitations the authors state:
  • Because the study was observational, it cannot determine causality.
  • The association may run the other way: dying patients may be more likely to develop pleural infection.
  • Performance status and tumour histological type were not available, which may have introduced confounding.
  • There was no information on the bacteria causing the infections, which may have masked an effect of a single organism.
  • Disease site was not specified for many cases, and results might have differed if it had been recorded for all patients.

Topics

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

Medical terms in this study, explained in our Lexicon: Mesothelioma, Cohort Study, Chemotherapy, Thoracic Surgery, Median Survival.

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