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The clinical effectiveness and cost-effectiveness of computed tomography screening for lung cancer: systematic reviews |
Black C, Bagust A, Boland A, Walker S, McLeod C, De Verteuil R, Ayres J, Bain L, Thomas S, Godden D, Waugh N |
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CRD summary This review concluded that there is insufficient evidence regarding the clinical effectiveness of screening for lung cancer using computed tomography. These conclusions are likely to be reliable. Authors' objectives To review the clinical effectiveness of computed tomography (CT) screening for lung cancer. Searching MEDLINE, EMBASE, the Cochrane Library, NHS EED, HTA, DARE, Bandolier, HMIC, the American Society of Clinical Oncology, Research Findings Electronic Register, National Horizon Scanning Centre, Science Citation Index, Web of Science Proceedings, National Research Register and the INAHTA register of projects were searched from January 1994 to January 2005; the search strategy was reported in full. The search was not restricted by language, but only English language studies were included in the review; studies published in other languages were noted. Systematic reviews were used as a source of relevant studies. The reference lists of included studies were also screened for additional relevant studies. Study selection Study designs of evaluations included in the reviewRandomised controlled trials (RCTs), case-control studies and cohort studies were eligible for inclusion. Specific interventions included in the reviewStudies of the use of CT to screen for lung cancer were eligible for inclusion. Only the CT screening arm was used from studies with an alternative screening tool as the comparator. Studies that assessed CT for diagnostic or staging purposes were excluded. Screening was either annual, biannual or 18 monthly, or a single CT screen. Reference standard test against which the new test was comparedNo inclusion criteria relating to the reference standard were specified. The studies included were not primary test accuracy studies, but some did provide data that could be used to estimate accuracy. Verification of positive CT scans was by tissue biopsy surgery or contrast-enhanced CT. Verification of negative CT results was by the absence of disease over a prolonged period, or at follow-up screening. Participants included in the reviewStudies conducted in the context of mass-population screening programmes were eligible for inclusion. All studies included participants aged at least 40 years, and most were restricted to smokers. One study was conducted in nuclear fuel workers, another among asbestos-exposed workers, and one included patients with atypical sputum cytology and chronic obstructive pulmonary disease. Outcomes assessed in the reviewThe primary outcomes of interest were lung cancer mortality and total mortality. How were decisions on the relevance of primary studies made?Two reviewers independently screened titles and abstracts for inclusion; relevant papers were retrieved and reviewed independently by two reviewers. Any disagreements were resolved by consensus. Assessment of study quality Studies were assessed for validity using the checklists reported in CRD Report 4. The authors did not state how many reviewers performed the validity assessment. Data extraction Data were extracted on incidence of non-calcified nodules (NCN) and lung cancer, and on histology and survival, and adverse events. The authors did not state how many reviewers performed the data extraction. Methods of synthesis How were the studies combined?A narrative synthesis was presented. How were differences between studies investigated?Differences between the studies were discussed in the text and study details were tabulated. The following a priori defined subgroups were discussed separately: age, gender, smoking status and occupation. Results of the review Twelve studies reported in 29 publications were included (at least n=25,749 baseline CT screening; n=54,342 CT examinations in total).
None of the studies provided information on the representativeness of the populations studied: all were conducted in volunteers and it was unclear how well these represented the general population. The duration of follow-up was limited to 2 years or less in most studies. Since the majority of studies did not include a comparator group, it was not possible to determine the effectiveness of screening in terms of changes in mortality.
Positive CT examinations.
The number of positive screens during the baseline examination ranged from 5.1 to 51% (12 studies). The proportion of positive screens on subsequent screening examinations was lower in the 7 studies that provided data on this (2.7 to 11.5%). The number- needed-to-screen to detect one lung cancer ranged from 31 to 249.
Detection of lung cancer and stage of disease.
The proportion of screen-positive patients who went on to receive a diagnosis of lung cancer ranged from 1.8 to 32%; most identified at baseline were stage 1 disease (53 to 100%). For tumours identified at subsequent screening, 63 to 100% were stage 1. Where reported (8 studies), the resectability of tumours detected by screening was high (>80% in most studies).
Test accuracy results.
Although not diagnostic accuracy studies, it was possible to derive some data on accuracy as information was provided on the proportion of test-positive results found to be truly positive based on histological confirmation. The positive predictive value was less than 20% in all studies that reported sufficient information to calculate this, reflecting the high false-positive rate associated with CT screening. From studies where it was possible to make some estimation of the number of false-negative results (generally based on clinical follow-up), the sensitivity of CT was estimated to be around 80 to 90%. Cost information A table of example costs for CT screening was presented: the reported estimates ranged from US$14 to US$507. Authors' conclusions There is insufficient evidence on whether CT screening can reduce mortality from lung cancer. CRD commentary This review was limited as the studies included were not of appropriate designs to answer the review objective. This was a limitation of the primary studies rather than of the review itself. The review question was focused and supported by defined inclusion criteria. An extensive literature search was conducted. However, only English language papers were included in the review, potentially introducing language bias. Few details of the review process were reported; only the study selection stage was reported as being conducted in duplicate, thereby reducing the potential for selection bias. A quality assessment was carried out and the results reported in full, for each study, in data extraction tables. The narrative synthesis was appropriate given the nature of the results. The authors' conclusions are supported by the results presented. Implications of the review for practice and research Practice: The authors stated that the clinical effectiveness of using CT to screen for lung cancer remains unclear.
Research: The authors identified three areas where further research is needed. Specifically: evidence from controlled trials on whether CT screening reduces mortality from lung cancer for either the whole population or for specific subgroups; better information on the epidemiology and natural history of screening-detected lung cancers; and information on the effects of early detection on morbidity and the quality-of-life effects of a positive screen while waiting for a diagnosis. Funding NHS R&D Health Technology Assessment (HTA) Programme, project number 04/41/01. Bibliographic details Black C, Bagust A, Boland A, Walker S, McLeod C, De Verteuil R, Ayres J, Bain L, Thomas S, Godden D, Waugh N. The clinical effectiveness and cost-effectiveness of computed tomography screening for lung cancer: systematic reviews. Health Technology Assessment 2006; 10(3): 1-106 Other publications of related interest Black C, de Verteuil R, Walker S, Ayres J, Boland A, Bagust A, Waugh N. Population screening for lung cancer using computed tomography, is there evidence of clinical effectiveness? A systematic review of the literature. Thorax 2007;62:131-8. Indexing Status Subject indexing assigned by NLM MeSH Adult; Aged; Aged, 80 and over; Cost-Benefit Analysis; Great Britain /epidemiology; Lung Neoplasms /diagnosis /mortality /radiography; Mass Screening /economics; Middle Aged; Program Evaluation; Quality of Health Care; Randomized Controlled Trials as Topic; State Medicine; Tomography, Emission-Computed AccessionNumber 12006008234 Date bibliographic record published 21/08/2006 Date abstract record published 09/08/2008 Record Status This is a critical abstract of a systematic review that meets the criteria for inclusion on DARE. Each critical abstract contains a brief summary of the review methods, results and conclusions followed by a detailed critical assessment on the reliability of the review and the conclusions drawn. |
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