Pleural plaques in lung cancer screening by low-dose computed tomography: prevalence, association with lung cancer and mortality

Our plain-English summary of Pleural plaques in lung cancer screening by low-dose computed tomography: prevalence, association with lung cancer and mortality, by M. Silva, N. Sverzellati, D. Colombi, et al (BMC Pulmonary Medicine, 2017).

The study

• Authors: M. Silva, N. Sverzellati, D. Colombi, G. Milanese, C. La Vecchia, C. Galeone, A. Marchianò, U. Pastorino
• Journal: BMC Pulmonary Medicine
• Published: 2017;17(1):155
• Cited by: 10 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Background: To report the prevalence of pleural plaques in a lung cancer screening trial by low-dose computed tomography (LDCT) and to test the association with incidence of lung cancer and mortality.

Methods: The LDCT of 2303 screenees were retrospectively reviewed with the specific aim of describing the prevalence and features of pleural plaques. Self-administered questionnaire was used to assess asbestos exposure. Frequency of lung cancer, lung cancer mortality, and overall mortality were detailed according to presence of pleural findings. Statistical analyses included comparison of mean or median, contingency tables, and Cox model for calculation of hazard ratio (HR) and its 95% confidence interval (CI).

Results: Among male screenees, 31/1570 (2%) showed pleural abnormalities, 128/1570 (8.2%) disclosed asbestos exposure, 23/31 (74.2%) subjects with pleural plaques consistently denied exposure to asbestos. There was a trend for higher frequency of lung cancer among subjects with pleural plaques (9.7% vs 4.2%). Lung cancer in subjects with pleural plaques was always diagnosed in advanced stage. Subjects with pleural plaques showed HR 5.48 (95% CI 1.61-18.70) for mortality from lung cancer.

Conclusions: Pleural plaques are a risk factor for lung cancer mortality that can be detected in lung cancer screening by LDCT, also in subjects that are not aware of asbestos exposure.

Trial Registration: NCT02837809 - Retrospectively registered July 1, 2016 - Enrolment of first participant September 2005.

In plain English

This study reviewed the first low-dose CT scans of 2303 current and former smokers in the Italian MILD lung cancer screening trial for pleural plaques. It then compared lung cancer and deaths in people with and without plaques. Asbestos exposure was recorded by a self-completed yes-or-no questionnaire. Plaques were seen in 31 of 1570 men (2.0%) and 2 of 733 women (0.3%), and the analyses covered men only. Of the 31 men with plaques, 23 (74.2%) consistently denied asbestos exposure. Lung cancer was diagnosed in 3 of 31 men with plaques (9.7%) and 65 of 1539 men without plaques (4.2%), a difference that was not statistically significant. All three cancers in men with plaques were stage 4. After adjustment for age, body mass index, pack-years and self-reported exposure, men with plaques had a hazard ratio of 5.48 (95% CI 1.61 to 18.70) for death from lung cancer. The authors concluded that pleural plaques are a risk factor for lung cancer mortality that screening can detect, also in people unaware of exposure. They noted that the questionnaire is known to be inconsistent.

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: Retrospective review of baseline low-dose CT scans from the screening (early detection) arm of a randomized lung cancer screening trial, with follow-up of lung cancer and deaths
• Who was studied: 2303 of the 2376 participants in the early detection group of the Multicenter Italian Lung Detection (MILD) trial (1570 men and 733 women). Participants were current or former smokers aged 50 to 75 with at least 20 pack-years, enrolled September 2005 to January 2011, with data updated to April 2016. Statistical analyses were done on the 1570 men only.
• Exposure: Pleural plaques (including diffuse pleural thickening) seen on baseline low-dose CT, and self-reported asbestos exposure from a yes-or-no questionnaire repeated at screening visits. No fiber types, jobs or doses were recorded.
• Main results:
  • Pleural plaques were found in 33 of 2303 subjects (1.4%): 31 of 1570 men (2.0%) and 2 of 733 women (0.3%).
  • Among men, 128 of 1570 (8.2%) consistently reported asbestos exposure. Self-reported exposure was significantly related to plaques (8 of 31, 25.8%, in men with plaques vs 120 of 1539, 7.8%, in men without; p = 0.003). Even so, 23 of 31 men with plaques (74.2%) consistently denied exposure.
  • Lung cancer was diagnosed in 3 of 31 men with plaques (9.7%; 1079 per 100,000 person-years) and 65 of 1539 men without plaques (4.2%; 456 per 100,000 person-years). The difference was not statistically significant (p = 0.148). The adjusted hazard ratio for lung cancer incidence was 1.84 (95% CI 0.57 to 5.93).
  • All three men with plaques who developed lung cancer had stage 4 disease.
  • Lung cancer deaths occurred in 3 of 31 men with plaques (9.7%) and 24 of 1539 men without plaques (1.6%), p = 0.015. The hazard ratio for lung cancer death in men with plaques was 5.48 (95% CI 1.61 to 18.70), adjusted for age, body mass index, pack-years and self-reported asbestos exposure.
  • In men with plaques, the hazard ratio was 2.02 (95% CI 0.73 to 5.56) for overall mortality and 0.70 (95% CI 0.10 to 5.10) for death from causes other than lung cancer. Deaths from other causes were 1 of 31 men with plaques vs 59 of 1539 without.
  • One mesothelioma was diagnosed, in a subject who had neither pleural plaques nor reported asbestos exposure.
• The authors' conclusion: The authors concluded that pleural plaques are a risk factor for lung cancer mortality that can be detected in low-dose CT lung cancer screening, also in subjects who are not aware of asbestos exposure. They suggested plaques could be considered in risk models.
• Limitations the authors state:
  • Asbestos exposure was assessed by a self-administered questionnaire, which the authors note is known to be inconsistent for assessing asbestos exposure.
  • Exposure was not investigated further in subjects who had plaques but were unaware of asbestos exposure.
  • Exposure was recorded with a yes-or-no question, without duration or intensity.
  • Signs of asbestos exposure in the lung tissue itself (parenchymal signs) were not investigated, although they are associated with lung cancer risk.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Lung cancer, Pleural plaques and thickening.

Medical terms in this study, explained in our Lexicon: Pleural Plaques, Low-Dose CT Screening, Lung Cancer, Asbestos Exposure, Hazard Ratio, confidence interval.

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