Lung and pleural CT signs predict deaths: 10-year follow-up after lung cancer screening of asbestos-exposed workers

Our plain-English summary of Lung and pleural CT signs predict deaths: 10-year follow-up after lung cancer screening of asbestos-exposed workers, by T. Vehmas, P. Oksa, L. Kivisaari (International Archives of Occupational and Environmental Health, 2012).

The study

• Authors: T. Vehmas, P. Oksa, L. Kivisaari
• Journal: International Archives of Occupational and Environmental Health
• Published: 2012;85(2):207-13
• Cited by: 12 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Purpose: To work out the predictive value of pathological (HR)CT signs concerning long-term mortality among those screened for lung cancer.

Methods: Five hundred and eighty four construction workers (574 males, 10 females) were originally screened for lung cancer and found negative. Their images were also scored for several lung and pleural signs. Mortality data were checked from the National Registry of Causes of Death. Cox regression adjusted for age, sex, smoking, BMI, and asbestos exposure was used to explore the relations between the radiological signs and deaths. The mean follow-up time was 10.53 years (0.56-12.98 years) and a total of 6,150 person years were followed up.

Results: Altogether, 185 deaths occurred (64 cardiovascular, 51 cancer, 24 non-cancer respiratory deaths, and 46 deaths from other causes). All studied emphysema signs were significant predictors of all-cause deaths as were most fibrosis signs (subpleural nodules, septal lines, parenchymal bands, and honeycombing), ground-glass opacities, thickened bronchial walls, pleural plaque extent, and adherences. Cardiovascular deaths were significantly associated with paraseptal emphysema and bullae. Several lung/pleural signs also predicted cancer and respiratory deaths.

Conclusion: Pathological lung/pleural CT signs found in screening seem to predict deaths in long term, which may require more careful medical surveillance of such individuals. Further studies are needed to generalize the present findings to general population.

In plain English

This Finnish study examined whether chest CT findings predicted later deaths among asbestos-exposed construction workers. The 584 workers (574 men, 10 women) had been screened for lung cancer with CT in 1996–1997 and found negative. Deaths were traced in the national death register over a mean of 10.53 years. There were 185 deaths: 64 cardiovascular, 51 cancer, 24 non-cancer respiratory and 46 from other causes. With each sign studied separately and adjusted for age, sex, body mass index, smoking and years of asbestos exposure, all emphysema signs, most fibrosis signs, ground-glass opacities, thickened bronchial walls, pleural plaque extent and pleural adherences predicted death from any cause. When all signs were analysed together, only honeycombing, paraseptal emphysema and pleural plaque extent remained significant. For plaque extent, the hazard ratio was 1.203 (95% CI 1.046–1.383) per one-standard-deviation increase. Several signs also predicted cardiovascular, cancer and non-cancer respiratory deaths. The authors concluded that these CT signs predicted deaths over the long term. They also said the causal link was obscure, and that they lacked information on blood pressure, cholesterol, diet, alcohol use and physical activity.

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: Follow-up (cohort) study of workers previously screened for lung cancer with CT. Lung and pleural signs scored on the baseline scans were related to later deaths using Cox regression, with each sign converted to z-scores. Mean follow-up was 10.53 years.
• Who was studied: 584 asbestos-exposed construction workers (574 men, 10 women) from the Helsinki area, Finland. They were screened with CT for lung cancer in 1996–1997, and those with a screen-detected malignancy were excluded. Mean age at CT was 63 years.
• Exposure: Occupational asbestos exposure as construction workers, mean duration 26 years (range 2–48). Fiber types are not specified. The factors studied as predictors were the lung and pleural signs seen on CT.
• Main results:
  • 185 deaths occurred among the 584 workers: 64 cardiovascular, 51 cancer, 24 non-cancer respiratory and 46 from other causes.
  • Compared with the general Finnish male population aged 60–79, deaths in this group were over-represented for all cancer (28% vs 23%), intrathoracic malignant neoplasms (12% vs 9%) and non-cancer respiratory causes (13% vs 8%).
  • Studied separately and adjusted for sex, age, body mass index, pack-years and asbestos exposure years, all emphysema signs predicted all-cause deaths, as did most fibrosis signs, ground-glass opacities and thickened bronchial walls.
  • Among the pleural signs, plaque extent and pleural adherences significantly predicted all-cause deaths.
  • With all signs in one model, honeycombing (HR 1.259; 95% CI 1.116–1.420), paraseptal emphysema (HR 1.255; 95% CI 1.110–1.418) and pleural plaque extent (HR 1.203; 95% CI 1.046–1.383) were the only significant predictors of all-cause mortality. Each hazard ratio is per one-standard-deviation (z-score) increase in the sign, not per unit of the original scale.
  • Cardiovascular deaths were associated with paraseptal emphysema (HR 1.317; 95% CI 1.112–1.560, P = 0.001) and bullae (HR 1.193; 95% CI 1.013–1.406, P = 0.034).
  • Cancer deaths excluding respiratory cancer were predicted by the presence of pulmonary nodules (HR 3.166, 95% CI 1.279–7.841, P = 0.013).
  • The 22 deaths from intrathoracic malignant neoplasms were significantly predicted by fibrosis signs, centrilobular emphysema, ground-glass opacities, thickened bronchial walls and bronchiectasis.
  • For non-cancer respiratory deaths, centrilobular emphysema, panlobular emphysema, pleural plaque extent and bronchial wall thickness remained significant predictors when all signs were analysed together.
• The authors' conclusion: The authors concluded that several pathological CT signs in this screened cohort predicted all-cause and cause-specific deaths over the long term. They said the causal link between the signs and mortality is obscure, and that the signs are more likely manifestations of other processes responsible for the deaths.
• Limitations the authors state:
  • No information on life habits, blood pressure or cholesterol levels, so these could not be controlled for.
  • Dietary habits, alcohol use and leisure-time physical activity were not collected and could not be adjusted for.
  • Bronchiectasis was rare, which limited the statistical power for that sign.
  • Further studies in other populations are needed to confirm and generalize the results.

Topics

Medical terms in this study, explained in our Lexicon: Low-Dose CT Screening, Lung Cancer, Asbestos Exposure, Emphysema, Fibrosis, Honeycombing, Pleural Plaques.

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