Our doctors recommend screening for people based on their age and the number of years they’ve smoked.
- People between the ages of 55 and 74 with no history of cancer or who have been cancer free for five years* and who have smoked at least one pack of cigarettes per day for 30 years (a marker referred to as 30 pack years) should be screened with low-dose helical CT of the chest.
- Such individuals should have low-dose CT of the chest once a year for a total of three years.
*The requirement of having no cancer history or being cancer free for five years does not apply to individuals with non-melanoma skin cancer.
We also recommend smoking cessation counseling or referral for all current smokers.
A pack year is a term used to describe the number of cigarettes a person has smoked over his or her lifetime. One pack year is defined as 20 cigarettes – one pack – smoked per day for one year.
People who’ve been diagnosed with cancer are at high risk for developing additional cancers for a variety of reasons: exposure to environmental factors (such as cigarette smoke) that predispose them to numerous cancers; effects of cancer therapy; and, possibly, shared genetic factors among different cancers.
Therefore, if you’ve had cancer that has been cured or brought under control and have a reasonable life expectancy, you should undergo screening that’s proven to be beneficial in the general population. Modifications to the screening program (starting at an earlier age, being screened more frequently) may need to be made, and methods of screening not necessarily recommended for everyone may be used. Our experts or your primary care doctor can help you make these decisions.
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.