Lung cancer screening with low-dose CT

Our plain-English summary of Lung cancer screening with low-dose CT, by S. Diederich, D. Wormanns, W. Heindel (European Journal of Radiology, 2003).

The study

• Authors: S. Diederich, D. Wormanns, W. Heindel
• Journal: European Journal of Radiology
• Published: 2003;45(1):2-7
• Type of article: Meta-analysis
• Cited by: 36 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Screening for lung cancer is hoped to reduce mortality from this common tumour, which is characterised by a dismal overall survival, relatively well defined risk groups (mainly heavy cigarette smokers and workers exposed to asbestos) and a lack of early symptoms. In the past studies using sputum cytology and chest radiography have failed to demonstrate any reduction in lung cancer mortality through screening. One of the reasons is probably the relatively poor sensitivity of both these tests in early tumours. Low radiation dose computed tomography (CT) has been shown to have a much higher sensitivity for small pulmonary nodules, which are believed to be the most common presentation of early lung cancer. As, however, small pulmonary nodules are common and most are not malignant, non-invasive diagnostic algorithms are required to correctly classify the detected lesions and avoid invasive procedures in benign nodules. Nodule density, size and the demonstration of growth at follow-up have been shown to be useful in this respect and may in the future be supplemented by contrast-enhanced CT and positron emission tomography. Based on these diagnostic algorithms preliminary studies of low-dose CT in heavy smokers have demonstrated a high proportion of asymptomatic, early, resectable cancers with good survival. As, however, several biases could explain these findings in the absence of the ultimate goal of cancer screening, i.e. mortality reduction, most researchers believe that randomised controlled trials including several 10000 subjects are required to demonstrate a possible mortality reduction. Only then general recommendations to screen individuals at risk of lung cancer with low-dose CT should be made. It can be hoped that international cooperation will succeed in providing results as early as possible.

In plain English

This article was a review, not a new study. The authors summarised the background for lung cancer screening with low-dose computed tomography (CT) and recent screening studies. They named cigarette smoking and asbestos exposure as risk factors, but the studies they reviewed enrolled heavy smokers, not asbestos-exposed workers specifically. The review reported that earlier screening with sputum cytology and chest X-rays failed to show fewer lung cancer deaths. In the first-round CT studies reviewed, lung cancer was found in 0.43% and 0.48% of people screened in two Japanese studies and up to 2.7% in a US study. Between 63% and 93% of detected cancers were stage I non-small cell lung cancer, and benign lesions accounted for less than 25% of invasive procedures. The authors wrote that these studies could not show that CT screening reduces lung cancer deaths, because biases could explain the findings. They also reported model calculations suggesting that 30 000 to 50 000 heavy smokers must be randomised to show a statistically significant 20% fall in lung cancer deaths. They concluded that proof from randomised trials should be awaited before general screening recommendations are made.

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: Narrative review of lung cancer screening with low-dose CT
• Who was studied: Published feasibility studies of low-dose CT screening in heavy smokers: ALCA and Shinshu (Japan), ELCAP and Mayo (USA), and the authors' own Münster study (Germany), with 1369, 3967, 1000, 1520 and 817 volunteers at baseline. The review also described randomised trials planned or starting as of July 2002.
• Exposure: No exposure was studied directly. The review names cigarette smoking and asbestos exposure as risk factors for lung cancer. The screening studies it reviewed enrolled heavy smokers.
• Main results:
  • Earlier studies of screening with sputum cytology with or without chest radiography, as reviewed, found more early tumours in screened subjects but failed to show reduced lung cancer mortality.
  • In the baseline (first-round) CT studies reviewed, the proportion of asymptomatic lung cancers found ranged from 0.43% and 0.48% in two Japanese studies up to 2.7% in a US study.
  • In the baseline CT studies reviewed, stage I non-small cell lung cancer made up 63% to 93% of detected cancers.
  • In all baseline studies reviewed, benign lesions were found in less than 25% of invasive procedures.
  • In the repeat (incidence) CT rounds reviewed, stage I non-small cell lung cancer made up 82% to 88% of detected cancers, except in one study that reported 33% based on only three incidence cancers.
  • The authors stated that the published screening studies could not establish that low-dose CT reduces lung cancer mortality.
  • The authors reported that model calculations suggest 30 000 to 50 000 heavy smokers would need to be randomised to show a statistically significant 20% mortality reduction.
• The authors' conclusion: The authors concluded that low-dose CT with appropriate diagnostic algorithms has been shown to detect many asymptomatic, early-stage, resectable non-small cell lung cancers, but that proof of benefit from controlled randomised trials should be awaited before general screening recommendations.
• Limitations the authors state:
  • The authors state that lead-time, length-time and overdiagnosis biases could explain the high proportion of early-stage cancers found by CT screening without any decrease in lung cancer mortality.
  • The authors note that findings at the first (baseline) CT are influenced by chance in when the scan happens relative to symptom onset.

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, Overall Survival, Sputum, Cytology.

Related studies

• Low-dose chest computed tomography screening of subjects exposed to asbestos — K. Kato, K. Gemba, et al. (2018)
• Yield of Low-Dose Computerized Tomography Screening for Lung Cancer in High-Risk Workers: The Case of 7189 US Nuclear Weapons Workers — S.B. Markowitz, A. Manowitz, et al. (2018)
• Impact of low-dose CT on lung cancer screening — S. Diederich, D. Wormanns (2004)
• Ultra-low-dose chest computer tomography screening of an asbestos-exposed population in Western Australia — F.J. Brims, C.P. Murray, et al. (2015)
• Asbestos Surveillance Program Aachen (ASPA): initial results from baseline screening for lung cancer in asbestos-exposed high-risk individuals using low-dose multidetector-row CT — M. Das, G. Mühlenbruch, et al. (2007)
• Impact of low-dose computed tomography screening on lung cancer mortality among asbestos-exposed workers — F. Barbone, F. Barbiero, et al. (2018)

Browse more research in European Journal of Radiology, or return to medical research.