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Lung Cancer Screening

Screening is testing done before any symptoms are noticeable. The purpose of screening is to catch cancer in its earliest, and most treatable, stages. Lung cancer causes more deaths than any other type of cancer, in part because it is most often found after it has spread.1

There are several factors, some controllable and others uncontrollable, which increase a person’s risk of developing lung cancer:

  • Smoking
  • Secondhand smoke exposure
  • Exposure to radon
  • Exposure to asbestos or other workplace carcinogens (substances that can increase the risk of developing cancer)
  • Family history of lung cancer
  • Previous radiation therapy to the breast or chest
  • Air pollution
  • Increasing age 1,2

High risk groups

There are multiple national organizations that have very similar, but sometimes slightly varying screening recommendations.  Screening recommendations are based on groups of people who fit certain criteria. Risk groups are broken into different categories and below is an example: 1,3

Risk Groups
Risk Criteria
Screening Recommendations
High Risk
  • >55 years old
  • >30 pack years* of smoking, and
  • Quit smoking
Screening is an option. People in this risk group should talk to their doctor about screening.
High Risk
  • >50 years old
  • >20 pack years of smoking, and
  • One other risk factor (except for secondhand smoke exposure)
Screening is an option. People in this risk group should talk to their doctor about screening
Moderate Risk
  • >50 years old
  • >20 pack years of smoking, or secondhand smoke exposure, and
  • No other risk factor
Screening is not recommended
Low Risk
  • >50 years old
  • >20 pack years of smoking
Screening is not recommended

*Pack years is a term used to help quantify the equivalent of how many years a patient has smoked. It is calculated by multiplying the number of packs of cigarettes smoked per day by the number of years the person has smoked. For example, smoking one pack per day for one year equals 1 pack year, whereas smoking two packs per day for two years equals 4 pack years.

Screening tools

Most experts recommend people at high risk for developing lung cancer get screened using spiral low-dose computed tomography (LDCT) of the chest. The LDCT takes several x-ray pictures of the body using different angles. While LDCT uses x-ray imaging, the amount of radiation is much lower than standard CT (computed tomography). This screening method is the only test proven through research to reduce the number of deaths from lung cancer. LDCT detects lung cancer better than chest x-ray, however there is a small risk of “false alarms,” where the test suggests there is cancer where there is not.1,4

After screening

The LDCT identifies nodules in the lungs. Nodules are small, round masses of tissue that can be caused by cancer, infections, scar tissue, or other conditions. Nodules caused by cancer appear differently on LDCT than nodules that are not cancerous (benign). Cancerous nodules are not likely to have calcium buildup, generally have rough edges and more unusual shapes, and they grow quickly and usually are larger in size than benign nodules.1

The first LDCT used in screening identifies nodules that are present in the lungs, whether cancerous or not. This scan is then considered the baseline for future tests, and doctors use it as a comparison to note any changes in size or density in future scans.1

Screening should occur every year for at least two years. Yearly screening may continue after two years, depending on the patient’s general health and their physician’s recommendation. Depending on the results of the first scan, some patients may be advised to repeat screening in 3-6 months.


Written by: Emily Downward | Last reviewed: January 2017.
  1. NCCN Guidelines for Patients. Lung Cancer Screening. Version Accessed online on 8/31/16 at
  2. Dela Cruz CS, Tanoue LT, Matthay RA. Lung cancer: epidemiology, etiology, and prevention. Clin Chest Med. 2011;32:605-644.
  3. Center for Disease Control. Lung Cancer Screening Recommendations. Accessed online on 8/31/16 at
  4. American Cancer Society. Accessed online on 8/25/16 at