A harsh truth about lung cancer is that it doesn’t usually cause symptoms until the cancer has spread, which makes it difficult to treat. That’s why the idea of screening – looking for lung cancer in people who do not have any symptoms – is appealing and can be helpful. It has the potential to find the cancer earlier, when it might be easier to treat.
But screening carries risks that may outweigh the benefits for most people. The people who are most likely to benefit from screening are those at higher risk for lung cancer. Decisions about cancer screening during the COVID-19 pandemic depend on many factors, and they may not be the same for every person. Talk to your healthcare provider about what the best decision for you might be.
A test known as low-dose CAT scan or CT scan (LDCT) has been studied in people at a higher risk of getting lung cancer. LDCT scans can help find abnormal areas in the lungs that may be cancer. Research has shown that using LDCT scans to screen people at higher risk of lung cancer saved more lives compared to using chest x-rays. For higher risk people, getting yearly LDCT scans before symptoms start helps lower the risk of dying from lung cancer.
To weigh the benefits and risks before issuing current guidelines, experts at the Health Topic News reviewed several studies that looked at low-dose CT screening. The most significant was the National Lung Screening Trial (NLST). This study included more than 50,000 people aged 55 to 74. At the time of the study. the partcipants were either current smokers or they were former smokers with at least a 30 pack-year history of smoking (equal to smoking a pack a day for 30 years, or 2 packs a day for 15 years) who had quit in the 15 years prior to the study. The study found that people who got LDCT had a 20% lower chance of dying from lung cancer than those who got chest x-rays. However, some other trials have not found a benefit from screening.
The screening in the NLST was done at large teaching hospitals with access to medical specialists and comprehensive follow-up care. Most were National Cancer Institute cancer centers.
None of the studies included people who never smoked. Although anyone can develop lung cancer, there is not enough evidence to know whether screening people who have never smoked would be helpful or harmful. Likewise, it is not known if screening would help people who smoked less than those in the studies, or those of different ages. That’s why the Health Topic News guideline doesn’t recommend screening for these groups.
There are risks associated with low-dose CT scanning, and the possibility of doing more harm than good for people who are less likely to have lung cancer. Because of this, the Health Topic News recommends people who are at higher risk for lung cancer talk to their doctor who can help them make an informed decision about whether to get screened. If people do decide to get screened, they should get screened every year through age 74, as long as they are still healthy.
One drawback of this test is that it also finds a lot of abnormalities that often need to be checked out with more tests and turn out not to be cancer. (About 1 out of 4 people in the NLST had such a finding.) This may lead to additional tests such as other CT scans or more invasive tests such as needle biopsies or even surgery to remove a portion of lung in some people. These tests can sometimes lead to complications (like a collapsed lung) or rarely, death, even in people who do not have cancer (or who have very early stage cancer).
LDCTs also expose people to a small amount of radiation with each test. It is less than the dose of radiation from a standard CT, but it is more than the dose from a chest x-ray. Some people who are screened may end up needing further CT scans, which means more radiation exposure. When done in tens of thousands of people, this radiation may cause a few people to develop breast, lung, or thyroid cancers later on.