Lung cancer is the leading cause of cancer death in the United States for both men and women. Most lung cancers are discovered at late stages, when treatment is more difficult. CT screening allows the diagnosis of lung cancer at its earliest and most treatable stages.
Not everyone should be screened for lung cancer.
CT scans are very sensitive tests that will pick up many “false positives“--- abnormalities in the lungs that are not cancer, and are unlikely to ever cause a problem. These findings may be small scars, enlarged blood vessels or tiny lymph nodes. However, when detected on CT, these abnormalities must be evaluated, which may cause anxiety. Evaluation will be either follow-up scans or rarely biopsies or other procedures, for what usually proves to be benign disease.
It is important to only screen individuals at increased risk for lung cancer. How do you know if you are at increased risk for lung cancer?
The single most important risk factor for lung cancer is cigarette smoking: Tobacco use accounts for almost 90% of all lung cancers. So if you have ever smoked, you have an increased chance of developing lung cancer. The longer you have been smoking and the more packs you have smoked, the greater the risk of developing cancer.
Most professional medical organizations now recommend consideration of annual lung cancer screening with low-dose CT scan for all individuals age 55-74 with at least a 30 pack-year smoking history (equivalent of 1pack/day for 30 years), especially if they continue to smoke, or quit within the last 15 years. Some groups also recommend screening for indivduals over 50 years of age with at least a 20 pack-year smoking history if they have additional risk-factors for lung cancer.
Additional risk factors that may put you at increased risk for lung cancer:
- Exposure to radon, a radioactive gas that can exist in houses.
- Exposure to asbestos, especially if exposure occurred in the workplace.
- Significant exposure to second hand smoke, either at home or at work.
- Exposure to cancer-causing agents in the environment, especially occupational exposures.
- Lung scarring from certain types of pneumonia or a diagnosis of COPD (chronic obstructive pulmonary disease) or emphysema.
- A first-degree relative, such as a parent or sibling, who has had lung cancer.
Additional Clinical Considerations
- Although the NLST trial published in 2011 showed that CT screening for lung cancer can save lives, and many questions remain, such as who will benefit most from screening, and how often should people be screened. The risk / benefit balance becomes increasingly unfavorable for lower risk individuals, such as nonsmokers.
- Some patients will undergo invasive diagnostic procedures as a result of lung cancer screening, in some cases these tests will lead to a diagnosis of cancer; in others they will confirm a benign condition. All invasive procedures have some risk of morbidity and mortality, and this must be considered before deciding to undergo screening.
- Potential harm from any screening program is the anxiety and concern resulting from false-positive tests, as well as possible invalid reassurance because of false-negative results. However, these harms have not been adequately studied.