Screening is the search for cancer in people who do not have any symptoms. At this time, some doctors may recommend testing in people who are at higher risk for lung cancer, such as current or former smokers, but not all doctors agree on this. No screening guidelines are available for symptomless people who have no lung cancer risk factors, and, therefore, screening isn't generally recommended.
There are three ways that doctors may try to screen for lung cancer:
Sputum cytology test
Spiral CT scans
For this test, you use a special jar to collect a sample of the mucus that you cough up, usually on a few mornings in a row, and take it to your doctor. Then, it’s checked for cancer cells under a microscope. Not all types of lung cancer will show cancer cells in the sputum.
This imaging test produces a picture of the organs within the chest. It gives a two-dimensional picture of the lungs.
This test is called a spiral CT scan for short. It uses X-rays to scan the whole chest. To have the test, you lie still on a table as it passes through the center of the CT scanner. It gives a detailed picture of what your lungs look like. A CT scan is painless and noninvasive, and requires no special preparation. You may be asked to hold your breath one or more times during the scan. While a CT scan can show some abnormal areas that a chest X-ray might miss, many of these areas turn out not to be cancer. But they may still require more invasive tests to be sure.
In earlier studies, neither sputum cytology nor chest X-rays were found to reduce the risk of death from lung cancer, which is why doctors haven't routinely recommended these tests. However, a recent large study found that spiral CT scans may indeed lower this risk. The National Lung Screening Trial (NLST) was a large clinical trial run by the National Cancer Institute. It compared spiral CT scans with chest X-rays in more than 50,000 people aged 55 to 74 who were current or former smokers with at least a 30-pack-year history of smoking (equal to smoking a pack a day for 30 years). People in the study got either yearly spiral CT scans or chest X-rays for three years. They were then followed for several years to see how many in each group died of lung cancer.
The study found that people who got spiral CT scans had a 20% lower chance of dying from lung cancer than those who got chest X-rays. But there are some questions that still need to be answered. For example, it's not clear if screening with spiral CT scans would have the same effect in people who smoked less (or not at all) or people younger than age 55. It's also not clear how often the scans should be done or how long they should be continued.
Spiral CT scans may also have some downsides that need to be considered. They also find a lot of abnormalities that turn out not to be cancer but that still need further testing to be sure. (About one out of four people in the NLST had such a finding.) This may lead to anxiety and possibly unnecessary tests such as more CT scans, or even more invasive tests such as biopsies or surgery in some people, when they don't have lung cancer. Spiral CT scans also expose people to a small amount of radiation during each test.
Some medical organizations, such as the American Society for Clinical Oncology, now recommend that doctors offer yearly spiral CT scans to people who would have met the entry criteria for the NLST. Other groups have not yet come out with screening guidelines since the publication of the study.
If you have risk factors for lung cancer, such as a history of smoking, talk with your doctor about whether you should consider using this test. The possible benefits, risks, and limitations of testing need to be taken into account when considering whether or not screening with spiral CT scans is right for you.