Progression of asbestosis predicts lung cancer

Our plain-English summary of Progression of asbestosis predicts lung cancer, by P. Oksa, M. Klockars, A. Karjalainen, et al (Chest, 1998).

The study

• Authors: P. Oksa, M. Klockars, A. Karjalainen, M.S. Huuskonen, K. Vattulainen, E. Pukkala, H. Nordman
• Journal: Chest
• Published: 1998;113(6):1517-21
• Cited by: 26 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Study Objectives: To explore whether the progression of asbestosis correlates with the risk of lung cancer among patients with asbestosis.

Design: A group of 85 asbestosis patients (78 men and 7 women) were radiographically followed up between 1979 and 1987. Two or three posteroanterior radiographs taken from each patient in 1978 to 1979, 1983 to 1984, and 1986 to 1987 were classified according to the International Labour Office 1980 classification and were used to divide the patients into progressors and nonprogressors. Follow-up for cancer was done automatically through the files of the Finnish Cancer Registry from the time of determination of the progression status to December 31, 1994. Predictors of lung cancer risk were studied with a logistic regression model, and the standardized incidence ratio (SIR) was calculated for lung cancer.

Results: Of the 24 male patients with progressive small opacity profusion, 11 (46%) developed lung cancer, as opposed to 5 (9%) of the 54 male patients without progression. The SIR for lung cancer was 37 (95% confidence interval, 18 to 66) for the progressors and 4.3 (1.4 to 9.9) for the nonprogressors. In both groups, all the lung cancer cases occurred among smokers or ex-smokers. None of the seven female patients showed progressive small opacity profusion. One of them developed lung cancer. In the logistic regression model including all 85 asbestosis patients, radiographic progression of small opacity profusion (p=0.0009) and current smoking (0.0021) were significant predictors of lung cancer morbidity.

Conclusions: Asbestosis patients with radiographic progression of small opacity profusion over a few years are at a higher risk of lung cancer than those with a less aggressive course of the disease. The progression of pulmonary fibrosis may be an independent risk factor that, in addition to smoking history and the intensity of asbestos exposure, could be used to estimate lung cancer risk.

In plain English

This Finnish cohort study asked whether asbestosis that worsens on chest X-rays is linked to lung cancer risk. The authors followed 85 asbestosis patients (78 men, 7 women) examined at the Finnish Institute of Occupational Health between 1979 and 1987. Two or three X-rays per patient, graded by the International Labour Office system, were used to sort patients into "progressors" and "nonprogressors". Lung cancers were then traced through the Finnish Cancer Registry to the end of 1994. Among the men, 11 of 24 progressors (46%) developed lung cancer, compared with 5 of 54 nonprogressors (9%). The standardized incidence ratio, which compares observed with expected cases, was 37 (95% confidence interval 18 to 66) for male progressors and 4.3 (1.4 to 9.9) for male nonprogressors. All lung cancers occurred in smokers or ex-smokers. In a statistical model, X-ray progression and current smoking both significantly predicted lung cancer. The authors concluded that progression of fibrosis may be an independent risk factor. They noted that the cohort was small and that they could not adjust for the amount smoked.

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: Cohort study: radiographic follow-up of asbestosis patients, with cancer follow-up through record linkage to the Finnish Cancer Registry, standardized incidence ratios, and logistic regression
• Who was studied: 85 asbestosis patients (78 men and 7 women) in Finland. They were drawn from 128 asbestosis patients who visited the Finnish Institute of Occupational Health for periodic examinations from 1979 to 1987, and they were the ones who visited at least twice. Cancer risk ratios were calculated for the men only.
• Exposure: Occupational asbestos exposure; the article does not name fiber types. Occupations were insulator, asbestos quarry worker, asbestos product factory worker, asbestos sprayer, and other. Mean years of exposure were 19 for progressors and 20 for nonprogressors. Smoking was also studied.
• Main results:
  • Among the men, 11 of 24 patients whose small opacity profusion progressed on X-ray (46%) developed lung cancer, compared with 5 of 54 men without progression (9%).
  • For the men, the standardized incidence ratio for lung cancer was 37 (95% CI 18 to 66) for progressors and 4.3 (95% CI 1.4 to 9.9) for nonprogressors.
  • For all the male asbestosis patients together, the standardized incidence ratio was 11, based on 16 observed lung cancers in 582 person-years.
  • All lung cancers occurred in smokers or ex-smokers. Among progressors, 80% of current smokers and 30% of ex-smokers developed lung cancer. Among nonprogressors, the figures were 20% and 7%.
  • None of the 7 women showed progression, and one of them developed lung cancer.
  • In logistic regression covering all 85 patients, X-ray progression of small opacities (p=0.0009) and current smoking (p=0.0021) were the significant predictors of lung cancer. The odds ratios were 9.6 (95% CI 2.53 to 36.8) for progression and 8.3 (95% CI 2.15 to 32.2) for current smoking.
  • Other cancers among the nonprogressors (men and women) included two mesotheliomas; the article does not state the site.
• The authors' conclusion: The authors concluded that asbestosis patients whose small opacity profusion progressed on X-ray over a few years were at higher risk of lung cancer than those with a less aggressive course. They also concluded that progression of fibrosis may be an independent risk factor, usable alongside smoking history and intensity of asbestos exposure to estimate lung cancer risk.
• Limitations the authors state:
  • The cohort was small and consisted of heavily exposed asbestosis patients.
  • The authors could not adjust for the amount of smoking.
  • ILO classification of small opacities is subject to variation between readers and within the same reader.
  • Patients in the highest ILO category (3) on the first X-ray were counted as nonprogressors by definition. The authors said this would tend to reduce the observed difference between groups.
  • Progression status was determined several years after diagnosis. Progressors were on average 5 years younger, which may mean they already had a faster course of disease before follow-up began.
  • Because only asbestosis patients were studied, the results say nothing about asbestos and lung cancer in people without 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: Lung Cancer, Cancer Registry, Standardized Incidence Ratio (SIR), confidence interval, Pulmonary Fibrosis, Asbestos Exposure.

Related studies

• Follow-up of asbestosis patients and predictors for radiographic progression — P. Oksa, M.S. Huuskonen, et al. (1998)
• Radiographic progression of asbestosis — H. Suoranta, M.S. Huuskonen, et al. (1982)
• Lung diffusing capacity relates better to short-term progression on HRCT abnormalities than spirometry in mild asbestosis — C.R. Nogueira, L.M. Nápolis, et al. (2011)
• Radiographic progression of asbestosis: preliminary report — A. Gregor, R.W. Parkes, et al. (1979)
• Low ERCC1 expression in malignant pleural mesotheliomas treated with cisplatin and vinorelbine predicts prolonged progression-free survival — Z.G. Zimling, J.B. Sørensen, et al. (2012)
• Progression free survival rate at 9 and 18 weeks predict overall survival in patients with malignant pleural mesothelioma: an individual patient pooled analysis of 10 European Organisation for Research and Treatment of Cancer Lung Cancer Group studies and an independent study validation — B. Hasan, L. Greillier, et al. (2014)

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