Health Technology Assessment 2006; Vol 10: number 3
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C Black,1* A Bagust,2 A Boland,3 S Walker,4 C McLeod,3 R De Verteuil,1 J Ayres,5 L Bain,1 S Thomas,1 D Godden6 and N Waugh1
1 Department of Public Health, University of Aberdeen, UK
2 University of Liverpool Management School, UK
3 Liverpool Reviews and Implementation Group (LRiG), University of Liverpool, UK
4 Department of Radiology, Aberdeen Royal Infirmary, UK
5 School of Medicine, Environmental and Occupational Medicine, University of Aberdeen, UK
6 School of Medicine, University of Aberdeen, UK
* Corresponding author
Screening for lung cancer has been the subject of debate for the past three decades. This has largely stemmed from the results of chest X-ray screening studies where improvements in survival were obtained but without reductions in disease-specific, or total, mortality. The debate raises two issues: the design of studies to evaluate screening for lung cancer, in particular the choice of comparator; and the potential role of over-diagnosis of well-differentiated, slow-growing tumours that would not have led to symptoms or death in the lifetime of the affected patient.
Lung cancer is the leading cause of death from cancer in the UK, killing approximately 34,000 people per year. By the time symptoms develop, the tumour is often at an advanced stage and the prognosis is bleak. Treatment at a less advanced stage of disease with surgical resection has been shown to substantially reduce mortality. Screening would be attractive if it could detect presymptomatic lung cancer at a stage when surgical intervention is feasible.
The aim of this review is to examine the clinical and cost-effectiveness of screening for lung cancer using computed tomography (CT) to assist policy making and to clarify research needs.
Fifteen electronic databases and Internet resources were searched from 1994 until December 2004/January 2005. In addition, bibliographies of the retrieved articles were searched and the register of projects held by the International Network of Agencies for HTA (INAHTA) was also checked.
Studies were included where screening for lung cancer was the principal theme of the paper. The initial search was for randomised trials in which survival in a group receiving CT screening was compared with a group not screened, but because of the lack of such studies, no restriction was placed on study type. Studies were reviewed by two authors independently.
Data extraction included details of the screening protocol, follow-up, diagnosis and participants. Information was sought about test characteristics, including sensitivity and specificity. The checklists and methods described in NHS Centre for Reviews and Dissemination (CRD) Report 4 were used for the quality assessment of studies.
Separate narrative summaries were performed for the clinical effectiveness and cost-effectiveness. Cost-effectiveness analysis resulting in a cost per quality-adjusted life-year was not feasible, therefore the main elements of such an appraisal were summarised and the key issues relating to the existing evidence base were discussed.
In total, 12 studies of CT screening for lung cancer were identified, including two randomised controlled trials (RCTs) and ten studies of screening without comparator groups. The quality of reporting of these studies was variable, but the overall quality was adequate. The two RCTs were of short duration (1 year) and therefore there was currently no evidence that screening improves survival or reduces mortality. The proportion of people with abnormal CT findings varied widely between studies (551%). The prevalence of lung cancer detected was between 0.4 and 3.2% (number need to screen to detect one lung cancer = 31249). Incidence rates of lung cancer were lower (0.11% per year). Detection of stage I and resectable tumours was high, 100% in some studies. Adverse events, as a result of investigation or surgery, or the screening process per se were poorly reported. Incidental findings of other abnormalities requiring medical follow-up were reported to be as high as 49%.
Six full economic evaluations of population CT screening programmes for lung cancer were included in the review. The magnitude of cost-effectiveness ratios reported vary widely. None was set in the UK and generalisation was complicated by wide variation in the data used in different countries and a paucity of UK data for comparison. All six made the fundamental assumption that screening with CT for lung cancer reduced mortality. At the current time, there is no evidence to support that assumption.
In the absence of evidence of health gains from screening for lung cancer, in terms of either quantity or quality of life, and faced with a range of uncertainties, from the frequency of abnormal screening findings within a population to the natural history of screening detected lung cancers, it is not feasible at the current time to develop accurately and meaningfully an economic argument for CT screening for lung cancer in the UK. For subgroups, in particular certain occupational groups, there is evidence of increased risk of lung cancer, but the role of screening has not been demonstrated by the current studies.
The accepted National Screening Committee criteria are not currently met, with no RCTs, no evidence to support clinical effectiveness and no evidence of cost-effectiveness.
In terms of what information is needed to assist decision-making about CT screening for lung cancer, the following research priorities were identified.
Black C, Bagust A, Boland A, Walker S, McLeod C, De Verteuil R, et al. The clinical effectiveness and cost-effectiveness of computed tomography screening for lung cancer: systematic reviews. Health Technol Assess 2006;10(3).
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The research reported in this monograph was commissioned by the HTA Programme as project number 04/41/01. The contractual start date was in September 2004. The draft report began editorial review in March 2005 and was accepted for publication in July 2005. As the funder, by devising a commissioning brief, the HTA Programme specified the research question and study design. The authors have been wholly responsible for all data collection, analysis and interpretation, and for writing up their work. The HTA editors and publisher have tried to ensure the accuracy of the authors report and would like to thank the referees for their constructive comments on the draft document. However, they do not accept liability for damages or losses arising from material published in this report.
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Editor-in-Chief: Professor Tom Walley
Series Editors: Dr Peter Davidson, Dr Chris Hyde, Dr Ruairidh Milne, Dr Rob Riemsma and Dr Ken Stein
Managing Editors: Sally Bailey and Sarah Llewellyn Lloyd
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