Our doctors recommend lung cancer screening for people based on their age and the number of years they’ve smoked.
We recommend screening if you:
- currently smoke or quit smoking within the past 15 years
- are between the ages of 50 and 80
- have smoked an average of one pack per day for at least 20 years, or the equivalent (for example, two packs a day for 10 years)
We also recommend smoking cessation counseling or referral for individuals who currently smoke.
Additional Information about CT Screening for Lung Cancer
Since this trial, there have been several studies that show the importance of expanded criteria for lung cancer screening. Learn more by visiting the US Preventive Services Task Force website.
The results of a study released in 2010 called the National Lung Screening Trial (NLST) showed that CT screening of high-risk individuals reduced their risk of dying from lung cancer. Until then, no organization recommended routine screening for lung cancer.
CT screening for lung cancer has only been studied in people at high risk of lung cancer — those with a long smoking history and who are 55 and older. For these individuals, the ten-year risk of developing lung cancer is greater than one in 100. For younger people and those with less smoking exposure, the risks are lower.
In the NLST, deaths from lung cancer decreased by 20 percent in a high-risk population of heavy smokers who had one scan each year for three years. These were low-dose helical (also known as spiral) CT scans of the chest that use x-rays to obtain a multiple-image scan of the entire chest during a single breath hold. Trial patients had no history of cancer in the preceding five years.
Individuals who are considering being screened for lung cancer with CT should know that the risks of the procedure have not been fully defined and that the benefit is relatively small.
In the study, for every 300 people who were screened, one death from lung cancer was averted. The risk that people who are screened with CT may develop other cancers as a result of the radiation wasn’t determined, but it’s likely to be far outweighed by the benefits of detecting lung cancer at an earlier, more treatable stage. Numerous studies do warn of other harms from CT screening, since the highly sensitive test can identify abnormalities that are not cancer. Finding these abnormalities can cause anxiety and lead to further ― unnecessary ― evaluation. In the first CT scan in the NLST study, such abnormalities were seen in one-quarter of patients. In other studies, the frequency has been as high as 40 to 50 percent of patients. Evaluation of these abnormalities can cause complications and can sometimes lead to unneeded operations during which a portion of the lung is removed.
The low-dose chest CT used for screening delivers a much lower amount of radiation than a conventional CT. The radiation dose of a low-dose CT scan is equivalent to about 15 chest x-rays and is five times lower than the dose from a conventional CT scan. The radiation dose of a low-dose CT can also be compared to about 50 cross-country flights or six months of natural background radiation.
Typically, a low-dose CT will deliver an effective dose of between 1 and 4 millisievert, whereas a conventional chest CT delivers an effective dose of about 5 to 20 millisievert, depending on the size of the patient. Studies are in progress to assess the lifetime risk of low-dose screening CT scans.
In the NLST study that began in 2002, the overall death rate from all causes was lower among the patients who underwent the three low-dose helical chest CT scans than in patients who had three chest x-rays instead.
Patients with cured or active cancer who are undergoing standard yearly surveillance chest CTs as part of their cancer care will not need an additional low-dose helical CT of the chest. For patients with active or cured cancer requiring chest CT surveillance, a low-dose helical CT of the chest is not a substitute. Nor is PET scan a substitute for a low-dose helical CT of the chest in patients appropriate for screening.