Abstract
BackgroundDiagnosis of lung cancer frequently occurs in its later stages. Low-dose computed tomography (LDCT) could detect lung cancer early.MethodsOur objective was to estimate the effect of LDCT lung cancer screening on mortality in high-risk populations. A systematic review of randomised controlled trials (RCTs) comparing LDCT screening programmes with usual care (no screening) or other imaging screening programme (such as chest X-ray (CXR)) was conducted. RCTs of CXR screening were additionally included in the network meta-analysis. Bibliographic sources including MEDLINE, Embase, Web of Science and the Cochrane Library were searched to January 2017. All key review steps were done by two persons. Quality assessment used the Cochrane Risk of Bias tool. Meta-analyses were performed.ResultsFour RCTs were included. More will provide data in the future. Meta-analysis demonstrated that LDCT screening with up to 9.80 years of follow-up was associated with a statistically non-significant decrease in lung cancer mortality (pooled relative risk (RR) 0.94, 95% confidence interval (CI) 0.74 to 1.19; p = 0.62). There was a statistically non-significant increase in all-cause mortality. Given the considerable heterogeneity for both outcomes, the results should be treated with caution.Network meta-analysis including the four original RCTs plus two further RCTs assessed the relative effectiveness of LDCT, CXR and usual care. The results showed that in terms of lung cancer mortality reduction LDCT was ranked as the best screening strategy, CXR screening as the worst strategy and usual care intermediate.ConclusionsLDCT screening may be effective in reducing lung cancer mortality but there is considerable uncertainty: the largest of the RCTs compared LDCT with CXR screening rather than no screening; there is imprecision of the estimates; and there is important heterogeneity between the included study results. The uncertainty about the effect on all-cause mortality is even greater. Maturing trials may resolve the uncertainty.
Highlights
Colorectal and Ovarian cancer screening trial (Lung) cancer is the most common cancer in the world with 1.8 million new cases diagnosed in 2012 [1]
From 9655 records identified in the searches, four Randomised controlled trial (RCT) were included in the meta-analysis of mortality data [8, 22,23,24,25] and a further two RCTs in the network metaanalysis [26,27,28] (Fig. 1)
Of the trials National Lung Screening Trial (NLST) stands apart, not just in terms of size with over 50,000 participants, but by Low-dose computed tomography (LDCT) being compared to chest x-ray (CXR) screening rather than no screening [8]
Summary
Lung cancer is the most common cancer in the world with 1.8 million new cases diagnosed in 2012 [1]. The prognosis for long-term survival with lung cancer is poor. The 1-year survival rate is over 80% when lung cancer is diagnosed in stage I, but under 20% when diagnosed in stage IV [5], this being due to the ability to treat surgically with curative intent at early stages. Few lung cancers present in their early stages, 25% in the UK National Lung Cancer Audit annual report 2016 [6]. Together, these facts suggest that there may be an opportunity to use secondary prevention by screening to increase the number of cancers identified at an early stage. Diagnosis of lung cancer frequently occurs in its later stages. Low-dose computed tomography (LDCT) could detect lung cancer early
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