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Major trial shows lung cancer screening mortality reduction

Screening for lung cancer using computed tomography (CT) screening detects more cancers and reduces mortality by 20% compared with chest radiography, a major trial has found.

A randomised controlled trial comparing low-dose CT screening with chest x-rays found there were 247 deaths from lung cancer per 100,000 person-years in the CT group and 309 deaths per 100,000 person-years in the radiography group – a 20% relative reduction in mortality.

The incidence of lung cancer was 645 cases per 100,000 person-years in the CT group compared with 572 cases per 100,000 person-years in the radiography group – a 13% increase in the incidence of cancer as detected by CT screening.

The National Lung Cancer Screening Trial (NLST) researchers concluded in the New England Journal of Medicine that ‘screening with the use of low-dose CT reduces mortality from lung cancer.'

The trial – conducted between August 2002 and April 2004 in more than 53,000 people in the US at high risk of lung cancer – is the first to demonstrate mass screening of high-risk groups could potentially improve lung cancer mortality.

It comes after Pulse revealed in February that the Department of Health had approved a pilot study, to begin this year, using CT scans to screen for lung cancer in up to 28,000 high-risk patients.

Eligible participants in the US trial were between 55 and 74 years old and had a history of cigarette smoking of at least 30 ‘pack years', and were randomly assigned to three years of annual screening with either low-dose CT or chest radiography.

During the screening phase of the trial, 39.1% of the participants in the low-dose CT group and 16.0% of those in the radiography group had at least one positive screening result. The percentage of all screening tests that identified a clinically significant abnormality other than an abnormality suspicious for lung cancer was more than three times as high in the low-dose CT group, at 7.5%, as in the radiography group, at 2.1%.

But the proportion of false positives in both groups was high, with a total of 96.4% of the positive screening results in the CT group and 94.5% in the radiography group false positives.

Dr Christine Berg, acting deputy director of the division of cancer prevention at the US National Cancer Institute in Bethseda, Maryland, concluded: ‘Before public policy recommendations are crafted, the cost-effectiveness of low-dose CT screening must be rigorously analyzed. The reduction in lung-cancer mortality must be weighed against the harms from positive screening results and overdiagnosis, as well as the costs.'

Professor John Field, lead investigator on the UK lung cancer screening pilot, said: 'The landmark NLST trial has demonstrated that CT is the first clinical tool that demonstrates a significant reduction in lung cancer mortality, in the USA. These initial results support the premise on which the UKLS trial has been developed.

'However, we await the outcome of the UK screening trial to guide National Health Service decision-makers on the future of lung cancer screening within the UK.'

NEJM 2011, published online 29 June

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