Chest CT scan screening for lung cancer in asbestos occupational exposure: a systematic review and meta-analysis

Our plain-English summary of Chest CT scan screening for lung cancer in asbestos occupational exposure: a systematic review and meta-analysis, by M. Ollier, A. Chamoux, G. Naughton, et al (Chest, 2014).

The study

• Authors: M. Ollier, A. Chamoux, G. Naughton, B. Pereira, F. Dutheil
• Journal: Chest
• Published: 2014;145(6):1339-1346
• Type of article: Meta-analysis, Systematic review
• Cited by: 66 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Objective: Lung cancer is the most frequent malignant asbestos-related pathology and remains the most fatal cancer of industrialized countries. In heavy smokers, early detection of lung cancer with chest CT scan leads to a 20% mortality reduction. However, the use of CT scan screening for early detection of lung cancer in asbestos-exposed workers requires further investigation. This study aimed to determine whether CT scan screening in asbestos-exposed workers is effective in detecting asymptomatic lung cancer using a systematic review and meta-analysis.

Methods: We reviewed all cohort studies involving chest CT scan screening in former asbestos-exposed workers. The search strategy used the following keywords: "asbestos," "lung cancer," "screening," and "occupation*" or "work." Databases were PubMed, Cochrane Library, Science Direct, and Embase.

Results: Seven studies matched our inclusion criteria. Baseline screening detected 49 asymptomatic lung cancers among 5,074 asbestos-exposed workers. Of the 49 reported lung cancers, at least 18 were in the earliest stage (stage I), accessible to complete removal surgery. The prevalence of all lung cancers detected by CT scan screening in asbestos-exposed workers was 1.1% (95% CI, 0.6%-1.8%).

Conclusions: CT scan screening in asbestos-exposed workers is effective in detecting asymptomatic lung cancer. Detection of lung cancer in asbestos-exposed workers using CT scanning is at least equal to the prevalence in heavy smokers (1%; 95% CI, 0.09%-1.1%) and also shared a similar proportion of stage I diagnoses. Screening asbestos-exposed workers could reduce mortality in proportions previously observed among heavy smokers and, thus, should not be neglected, particularly for individuals combining both exposures.

In plain English

This article was a systematic review and meta-analysis that pooled results from earlier studies. The authors did not screen anyone themselves. They looked for cohort studies in which former asbestos-exposed workers had chest CT scans, and they counted the lung cancers found at the first (baseline) scan. Seven studies met their criteria, covering 5,074 asbestos-exposed workers. Across those studies, 49 lung cancers were found in people without symptoms, and at least 18 were at the earliest stage (stage I). The share of workers found to have lung cancer ranged from 0.4% to 4.28% between studies. The pooled figure was 1.1% (95% CI, 0.6%-1.8%), and the studies' results differed markedly from one another. The authors compared this with the 1% (95% CI, 0.09%-1.1%, as printed) reported by a separate large trial in heavy smokers. They concluded that CT screening in asbestos-exposed workers is effective in detecting asymptomatic lung cancer. They noted that few studies were available and that exposure was described inconsistently. They also noted that smoking is a confounder and that later rounds of screening were not reported.

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: Systematic review and meta-analysis of cohort studies of chest CT screening. The primary outcome was the number of lung cancers diagnosed at the first (baseline) CT screening.
• Who was studied: Seven published cohort studies, with 187 to 1,119 participants each, totalling 5,074 former asbestos-exposed workers. The studies came from searches of PubMed, Cochrane Library, Science Direct and Embase on September 12, 2013. Participants were reported as aged between 58 and 68 years, and women made up 0.95% to 5.3% of participants (one study excluded women).
• Exposure: Occupational asbestos exposure, defined differently by each included study. No fiber types were specified for the screened workers. Mean exposure duration in five studies ranged from 17.7 to 30 years. Occupations, where given, included power plant work, construction work involving insulation, asbestos-containing panels or asbestos paints, asbestos-cement manufacturing, railway rolling stock fabrication, and insulation work in shipyards or elsewhere.
• Main results:
  • Across the seven studies, 49 lung cancers were detected at baseline screening among 5,074 asbestos-exposed workers.
  • The pooled prevalence of lung cancer detected by low-dose CT in asbestos-exposed workers was 1.1% (95% CI, 0.6%-1.8%).
  • Prevalence at baseline ranged from 0.4% to 4.28% between studies. The lowest was in the study with the shortest mean exposure (17.7 years). The highest was in a population combining heavy asbestos exposure (16-45 years) with smoking.
  • Of the 49 lung cancers, at least 18 were stage I. The proportion at stage I ranged from 20% to 100% between studies.
  • The seven studies' results were statistically heterogeneous (P = .002, I2 = 71.9).
  • Follow-up after diagnosis varied across the seven studies. In one study, all nine cancers were completely removed. In another, none of the five diagnosed people survived.
  • The authors compared the pooled figure with the lung cancer prevalence reported in a separate study, the largest available trial in heavy smokers: 1%; 95% CI, 0.09%-1.1% (as printed).
• The authors' conclusion: The authors concluded that CT scan screening in asbestos-exposed workers is effective in detecting asymptomatic lung cancer. They said detection was at least equal to that reported in heavy smokers, and they suggested screening could reduce mortality in proportions previously observed among heavy smokers.
• Limitations the authors state:
  • The meta-analysis was based on few studies, because most asbestos literature was published before 1990, when CT scanning was not common.
  • Inclusion criteria differed between studies in how asbestos exposure and smoking status were described. No atmospheric measurements existed from the time of exposure.
  • Smoking is a confounder, and it is hard to recruit enough nonsmoking asbestos-exposed workers.
  • None of the seven studies reported results from later rounds of CT screening.
  • There were too few early-stage detections for a meta-analysis of stage I cancers.

Topics

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

Medical terms in this study, explained in our Lexicon: CT Scan, Lung Cancer, Occupational Exposure, Systematic Review, Meta-Analysis, Pathology.

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• PET scan contribution in chest tumor management: a systematic review for thoracic surgeons — L. Duranti, F. Leo, et al. (2012)
• Ultra-low-dose chest computer tomography screening of an asbestos-exposed population in Western Australia — F.J. Brims, C.P. Murray, et al. (2015)
• CT scan screening for lung cancer: risk factors for nodules and malignancy in a high-risk urban cohort — A.K. Greenberg, F. Lu, et al. (2012)
• Smoking, occupational risk factors, and bronchial tumor location: a possible impact for lung cancer computed tomography scan screening — M. Gonzalez, J.M. Vignaud, et al. (2012)

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