Evidence Summary

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Low-dose computed tomography for lung cancer screening reduces lung cancer deaths and total deaths in current and former smokers with no symptoms

Humphrey LL, Deffebach M, Pappas M, et al. Screening for lung cancer with low-dose computed tomography: a systematic review to update the US Preventive services task force recommendation. Ann Intern Med. 2013;159:411-20.

Review question

What is the current evidence on screening for lung cancer with low-dose computed tomography (CT)?


CT uses computer-processed X-rays to create pictures (tomographic images) of selected areas of the body.

As early-stage lung cancer is associated with lower mortality than late-stage disease, early detection and treatment are beneficial.

How the review was done

This review updates the 2004 U.S. Preventive Services Task Force’s evidence on the effectiveness and harms of low-dose CT screening for lung cancer.

The researchers did a systematic review of 4 randomized controlled trials comparing low-dose CT screening for lung cancer with chest x-ray or usual care without low-dose CT.

Trials were the National Lung Screening Trial (NLST), Detection and Screening of Early Lung Cancer (DANTE), Danish Lung Cancer Screening Trial (DLCST), and Multicentric Italian Lung Detection (MILD).

Studies included current or former smokers, aged 49 to 74, with no symptoms. Follow-up was between 2.8 and 6.5 years for at least 50%of participants. Publication period was 2008 to 2012.

What the researchers found

The large NLST study included 53,454 people. After 6.5 years of follow-up, lung cancer deaths were reduced by 20% in the low-dose CT group compared with the control group (chest x-ray). Statistically, the mortality reduction in this trial could range between 7 and 27%.

The number of patients needed to screen to prevent 1 lung cancer death was 320 among participants who completed 1 screening.

Deaths from any cause were reduced by 6.7% (from 1.2 to 13.6%). The number needed to screen to prevent 1 death was 219.


The DANTE, DLCST, and MILD studies were much smaller (between 2,472 and 4,104 people). None showed benefit of low-dose CT compared with usual care (no low-dose CT).

Low-dose CT did not reduce overall quality of life or affect smoking rates.

Low-dose CT detected several incidental findings, such as emphysema and calcium build-up in the heart arteries.

Harms included radiation exposure, overdiagnosis (that is, a high rate of false-positive findings that were typically resolved with further imaging).


Low-dose computed tomography reduces lung cancer deaths and deaths from any cause in current and former smokers who do not show symptoms of the disease.



Control group
A group that receives either no treatment or a standard treatment.
A test result that suggests the presence of a disease which turns out not to be there.
Randomized controlled trials
Studies where people are assigned to one of the treatments purely by chance.
Systematic review
A comprehensive evaluation of the available research evidence on a particular topic.

Related Web Resources

  • Breast cancer: Risks and benefits, age 50-69

    Canadian Task Force on Preventive Health Care
    Your risk of dying from breast cancer is slightly reduced if you have regular screening. However, regular screening increases your chance of a false positive result, a biopsy and having part or all of a breast removed unnecessarily.
  • Breast cancer: Patient algorithm

    Canadian Task Force on Preventive Health Care
    The Canadian Task Force on Preventive Health Care recommends women between 50 and 74 years old who are not at high risk get screened for breast cancer every 2 to 3 years. Talk to your doctor about screening options if you are at high risk or over 74 years old.
  • Breast cancer: Patient FAQ

    Canadian Task Force on Preventive Health Care
    This resource includes frequently asked questions about breast cancer, including: Who is considered high risk? What are the harms associated with mammography? and Why is routine screening NOT recommended for women 40-49 years?
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