Screening means testing for a disease when there are no symptoms or history of that disease. Doctors give a screening test to find a disease early on, when treatment may work better. Scientists have studied several types of screening tests for lung cancer. A review of these studies by experts shows that more information is needed. It is not known if these tests can help prevent deaths from lung cancer.

Examples of screening tests for lung cancer include-

  • Chest X-rays.
  • Sputum cytology (looking for cancer cells in phlegm under a microscope).
  • CAT scans of the lungs (CAT scans are detailed images of the inside of the body, made by a computer that combines X-ray images taken from different angles).

There is fair evidence that low-dose CAT scans, chest X-rays, and sputum cytology can find cancers earlier than they would be found without screening, but there is little evidence that these screening tests actually prevent people from dying from lung cancer.

Screening also has its downside. Screening tests may find spots (abnormalities) in the lungs that are not cancers. However, a screening test does not always show the difference between cancers and other abnormalities that are not cancers. More tests may be needed to find out if the spot is a cancer. These tests might include removing a small piece of lung tissue for more testing (biopsy). This means that some people might have a surgical procedure even though they don't have cancer. These procedures have risks associated with them. They also can cause anxiety and cost money.

Experts do not know if the benefits of screening outweigh the potential harms. For these reasons, experts do not currently recommend for or against lung cancer screening. Screening for lung cancer with chest X-rays was once promoted by some experts, but researchers found out that people who were screened did not have a lower death rate than people who were not screened.

Studies are underway that will help provide more information about the effectiveness of more modern screening tests.