Impact of low-dose computed tomography screening on lung cancer mortality among asbestos-exposed workers

Our plain-English summary of Impact of low-dose computed tomography screening on lung cancer mortality among asbestos-exposed workers, by F. Barbone, F. Barbiero, O. Belvedere, et al (International Journal of Epidemiology, 2018).

The study

• Authors: F. Barbone, F. Barbiero, O. Belvedere, V. Rosolen, M. Giangreco, T. Zanin, F.E. Pisa, S. Meduri, A. Follador, F. Grossi, G. Fasola
• Journal: International Journal of Epidemiology
• Published: 2018;47(6):1981-1991
• Cited by: 19 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Background: We previously showed that low-dose computed tomography (LDCT) screening in asbestos-exposed workers is effective in detecting lung cancer (LC) at an early stage. Here, we evaluate whether LDCT screening could reduce mortality from LC in such a high-risk population.

Methods: Within a cohort of 2433 asbestos-exposed men enrolled in an Occupational Health surveillance programme, we compared mortality between the participants in the ATOM002 study (LDCT-P, N = 926) and contemporary non-participants (LDCT-NP, N = 1507). We estimated standardized mortality ratios for the LDCT-P and LDCT-NP populations using regional and national rates (SMR_FVG and SMR_ITA, respectively). We compared survival for all causes, all neoplasms, LC and malignant neoplasm of pleura (MNP) between LDCT-P and LDCT-NP using Cox proportional hazard models adjusted for age, smoking history, asbestos exposure level and comorbidities.

Results: A reduction in mortality from LC was observed in the LDCT-P group compared with regional and national figures (SMR_FVG = 0.55, 95% confidence interval (CI) 0.24-1.09; SMR_ITA = 0.51, 95% CI 0.22-1.01); this was not the case for the LDCT-NP group (SMR_FVG = 2.07, 95% CI 1.53-2.73; SMR_ITA = 1.98, 95% CI 1.47-2.61). A strong reduction in LC mortality was observed for the LDCT-P compared with the LDCT-NP [hazard ratio (HR) = 0.41, 95% CI 0.17-0.96]. Mortality was also reduced for all causes (HR = 0.61, 95% CI 0.44-0.84), but not for all neoplasms (HR = 0.97, 95% CI 0.62-1.50) and MNP (HR = 0.86, 95% CI 0.31-2.41) within the LDCT-P population.

Conclusions: In our cohort, participation in the LDCT screening study was associated with reduced mortality from LC. This finding supports the use of LDCT in surveillance programmes for asbestos-exposed workers.

In plain English

This cohort study followed 2433 asbestos-exposed men in an occupational health surveillance programme in Monfalcone, a shipbuilding town in north-east Italy. It compared 926 men who joined a low-dose CT (LDCT) lung cancer screening study called ATOM002, which enrolled them in 2002 and 2003, with 1507 men in the same programme who did not join. Deaths were tracked to the end of 2011. There were 8 lung cancer deaths among screened men and 50 among non-participants. After adjusting for age, smoking, asbestos exposure level and other illnesses, screened men had a lower risk of dying from lung cancer (hazard ratio 0.41, 95% CI 0.17 to 0.96) and from all causes (0.61, 95% CI 0.44 to 0.84). No difference was found for deaths from all cancers or from malignant neoplasm of the pleura. Deaths from pleural cancer were higher than in the general population in both groups. The authors concluded that taking part in screening was associated with lower lung cancer mortality. They noted that the study was not randomized and that screened men may have been healthier to begin with.

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 mortality study comparing men who took part in a prospective, non-randomized LDCT screening study (ATOM002) with men in the same surveillance programme who did not take part. It also compared both groups with regional and national death and cancer rates.
• Who was studied: 2433 asbestos-exposed men enrolled in the Monfalcone Occupational Health surveillance programme and living in the Friuli Venezia Giulia region of north-east Italy in early 2002. Of these, 926 took part in the ATOM002 LDCT screening study (enrolment February 2002 to October 2003) and 1507 were contemporary non-participants. Women were excluded because fewer than 4% of the programme's subjects were female. Mortality was followed to 31 December 2011 and cancer incidence to 31 December 2009.
• Exposure: Past occupational asbestos exposure, largely linked to the Monfalcone shipyards. Fiber types were not specified. An occupational health physician classed exposure level as high, medium or low from work history. The intervention compared was a baseline chest X-ray and LDCT followed by a second LDCT (913 of 926 participants, 98.6%, had one), against routine surveillance with clinic review and chest X-ray.
• Main results:
  • 58 lung cancer deaths were observed from 2002 to 2011: 8 among screening participants and 50 among non-participants.
  • Compared with regional rates, the lung cancer standardized mortality ratio was 0.55 (95% CI 0.24-1.09) for screening participants, an interval that includes 1. For non-participants it was 2.07 (95% CI 1.53-2.73).
  • Compared with national Italian rates, the lung cancer standardized mortality ratio was 0.51 (95% CI 0.22-1.01) for screening participants, an interval that includes 1. For non-participants it was 1.98 (95% CI 1.47-2.61).
  • In the adjusted comparison, screening participants had a lower risk of lung cancer death than non-participants: hazard ratio 0.41 (95% CI 0.17-0.96). The model was adjusted for age, Charlson-Quan comorbidity index, smoking and asbestos exposure level.
  • Screening participants also had lower all-cause mortality than non-participants: adjusted hazard ratio 0.61 (95% CI 0.44-0.84).
  • There was no difference in mortality from all neoplasms between participants and non-participants: adjusted hazard ratio 0.97 (95% CI 0.62-1.50).
  • There were 17 deaths from malignant neoplasm of the pleura: 6 among participants and 11 among non-participants. The adjusted hazard ratio was 0.86 (95% CI 0.31-2.41). Both groups had more such deaths than the regional population: SMR 4.85 (95% CI 1.59-10.57) in participants and 5.81 (95% CI 2.90-10.41) in non-participants.
  • Lung cancer incidence did not differ between groups: 16 cases among participants and 38 among non-participants, with an adjusted hazard ratio of 1.02 (95% CI 0.50-2.09).
• The authors' conclusion: The authors concluded that, in their cohort, taking part in the LDCT screening study was associated with reduced lung cancer mortality, and that this supports the use of LDCT in surveillance programmes for asbestos-exposed workers. They also concluded that approaches other than LDCT should be pursued for early diagnosis of malignant neoplasm of the pleura.
• Limitations the authors state:
  • There was no randomization, so selection bias is possible.
  • The study was not powered to compare mortality for outcomes other than lung cancer.
  • No data were available on lung cancer stage, so stage could not be compared between groups.
  • Asbestos exposure and cigarette smoking were not measured quantitatively, so results may be affected by residual confounding.
  • A 'healthy study participant' effect may partly explain the findings. Participants were younger, had fewer comorbidities and had more often quit smoking.

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: Low-Dose CT Screening, Lung Cancer, standardized mortality ratio (SMR), Neoplasm, Pleura, Asbestos Exposure, confidence interval, Hazard Ratio.

Related studies

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• Low-dose computed tomography screening for lung cancer and pleural mesothelioma in an asbestos-exposed population: baseline results of a prospective, nonrandomized feasibility trial--an Alpe-adria Thoracic Oncology Multidisciplinary Group Study (ATOM 002) — G. Fasola, O. Belvedere, et al. (2007)
• Predictive accuracy of the Liverpool Lung Project risk model for stratifying patients for computed tomography screening for lung cancer: a case-control and cohort validation study — O.Y. Raji, S.W. Duffy, et al. (2012)
• Psychological impact of computed tomography screening for lung cancer and occupational pulmonary disease among asbestos-exposed workers — T. Vierikko, S. Kivistö, et al. (2009)
• Ultra-low-dose chest computer tomography screening of an asbestos-exposed population in Western Australia — F.J. Brims, C.P. Murray, et al. (2015)
• Low-dose chest computed tomography screening of subjects exposed to asbestos — K. Kato, K. Gemba, et al. (2018)

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